Nervous and Endocrine systems

Functions

Response time

Functions:

1. Control and adjust the activities of others to achieve HOMEOSTASIS

2. Chemical communication with targeted tissues

Response:

1. Nervous system-swift and brief

2. slow and long

1. Sensing changes with sensory receptors

2. Interpreting and remembering those changes

3. Reacting to those changes with effectors

-muscular contractions

-glandular secretions

sense changes in the internal and external environment through sensory receptors

-done with sensory (afferent) neurons

analyze the sensory information, store some aspects, and make decisions regarding appropriate behaviors

-done by the association neurons in the CNS

respond to stimuli by initiating action

-done with motor (efferent) neurons

-Functional unit of the nervous system

-have the capacity to produce action potentials (electrical excitability)

-Cell body/soma: single neucleus with prominent nucleolus

-Cell processes=dendrites and axons

Dendrites: receiving portions of a neuron

Axon: conducts nerve impulses from the neuron to the dendrites or cell body of another neuron or to an effector organ

1. Anaxonic neuron-only found in CNS *Sensory info

2. Bipolar neuron-2 axons *special sensory info

3. Unipolar-1 axon with soma branched off *sensory info

4. Multipolar neuron-Soma at one end with axon following *motor response

1. Dendrites are stimulated

2. Stimulation passes through cell body

3. Axon hillock summates this stimulation and creates an action potential

4. Action potential travels on the axon to the synaptic terminals

5. Synaptic terminals release chemicals called neurotransmitters to effector or next neuron

Functional groups of neurons

(Functional classification)

1. Sensory neurons-mostly unipolar neurons

2. Motor neurons-mostly multipolar neurons

3. Interneurons (association neurons) CNS-mostly multipolar neurons

Neuroglia (glial cells)

Functions

1. Provide framework for neural tissue

2. Maintain intercellular environment

3. Act as phagocytes

(Support neurons)

1. Astrocytes

2. Oligodendrocytes

3. Microglia

4. Ependymal cells

Astrocytes

Functions

-largest and most numerous glial cells.

FUNCTIONS

a. maintain the blood-brain barrier (bbb)

b. Perform repairs in damaged neural tissue

c. Guide neuron development

d. Control interstitial environment (homeostasis)

-Myelinate axons with myelin in the CNS

-Works like insulation making action potentials travel down axons faster

-Myelin gives a white appearance-->white matter

*Clean up crew*

-Break down and remove cellular waste, debris and pathogens in the CNS

-In conjunction with capillaries, ependymal cells produce and maintain cerebral spinal fluid (CSF) in the brain

-Line the ventricles of brain and spinal cord

1. Satellite cells:regulate waste, nutrients, gases neurotransmitter levels around neurons

2. Schwann cells: Myelinate axons in the PNS, assist in repair after injury

1. Exteroceptors

2. Interoceptors

3. Proprioceptors

External environment

-Touch, temperature, pressure sensations

-Special senses (sight, smell, hear)

Internal environment

-Digestive, respiratory, cardiovascular, urinary, reproductive systems

-Deep pressure and pain sensations

Body position

-position and movement of skeletal muscles and joints

-information carried in somatic sensory neurons

1. Thermoceptors

2. Nociceptors

3. Mechanoreceptors

4. Chemoreceptors

5. Photoreceptors

6. Proprioceptors

Simplest type of pathway

-Pathways are specific neuronal circuits and include at least 1 synapse

Components of a reflex arc

process

1. Sensory receptor-arrival of stimulus

2. Sensory neuron-neuron activation

3. Interneuron (CNS)-info processing

4. Motor neuron-neuron activation

5. Effector organ (muscle or gland)-response

*In through dorsal side of spinal cord, out through ventral side*

1. Epineurium

2. Perineurium

3. Endoneurium

Outermost layer

-collagen fibers that cover entire nerve

Middle layer

-Around fascicles

S.A.M.E

D.A.V.E

Sensory is

Afferent

Motor is

Efferent

Dorsal is from

Afferent

Ventral is to

Efferent 

1. Central Nervous System (CNS)

2. Peripheral Nervous System (PNS)

-Brain and Spinal cord

-Integrating, processing, coordinating

-Intelligence, memory, learning, emotion

-Neural tissue outside the CNS (Nerves)

-Provides sensory info to the CNS

-Carries motor commands to peripheral tissues

-Afferent

-Efferent

Brain and spinal cord

*Command center

1. Afferent division

2. Efferent division

-brings sensory info to the CNS

1. Visceral Sensory-smooth muscle, cardiac muscle, glands

2. Somatic Sensory-skeletal muscles, joints, skin

-carries motor commands to muscles and glands

-begins inside the CNS and ends at an effector

1. Somatic motor (SNS)

2. Visceral motor (autonomic nervous system ANS)

-Controls skeletal muscle contractions

-Generally voluntary

-Regulates smooth muscle, cardiac muscle, glands

-Involuntary

1. Plasticity (structure) maintained throughout life

-sprouting of new dentrites

-synthesis of new proteins

-changes in synaptic contacts with other neurons

2. Limited ability for regeneration

-PNS can repair

-CNS cannot repair

-inhibition by neuroglial cells

-absence of growth stimulating factors

-lack of neurolemmas

-rapid formation of scar tissue

Epilepsy

CAUSES

-one of the most common neurological disorders

-Short recurrent attacks initiated by electrical discharges in brain IE lights, noise, or smells may be sensed; skeletal muscles may contract involuntarily; loss of consciousness

-Some CAUSES: brain damage at birth, metabolic disturbances, infections, toxins, vascular disturbances, head injuries, tumors

-Routine adjustments in the physiological systems

-regulates body temperature and coordinates cardiovascular, respiratory, digestive, excretory, and reproductive functions

*involuntary

Structural and functional components of ANS

-regulated by...

Structure: includes autonomic sensory neurons, integrating centers in the CNS, and autonomic motor neurons

Function: operates without conscious control

Regulated by the hypothalamus and brain stem

-contains sensory and motor neurons

-sensory neurons receive input from receptors of the special and somatic senses

-sensed are consciously perceived

-Somatic neurons innervate skeletal muscle to produce voluntary movements

-effect of a motor neuron is always excitation

-contains both sensory and motor neurons

-Receives sensory input from somatic senses and special sensory neurons

-Autonomic motor neurons regulate visceral activities by exciting/increasing or inhibiting/decreasing ongoing activities of cardiac muscle, smooth muscle, and glands

-Autonomic sensory neurons associated with interoceptors

-Involuntary-unconsciously percieved

Motor neuron pathways

Somatic vs Autonomic

Somatic motor neuron pathways= single motor neuron

Autonomic motor pathways=two motor neurons in series

*2 Motor neurons

1st- Cell body in CNS and myelinated axon extends to autonomic ganglion

**EXCEPT FOR ADRENAL GLAND**

2nd- Cell body in an autonomic ganglion and non-myelinated axon extends to effector

1. Sympathetic

2. Parasympathetic

*Organs that receive impulses from both are said to have dual innervation

1. preganglionic neurons in lateral horns of spinal segments T1-L2

2. Ganglia near spinal cord-

3. Target organs

*Fight or flight response*

1. Preganglionic neurons in brain stem and in lateral portion of anterior gray horns of S2-S4

AND CN III, VII, IX, X

2. Ganglia in or near target organs

3. Target organs

*Rest and relax response

1. Accelerate heartrate and blood flow

2. Stimulate energy production

3. Release stored lipids

4. Stimulate sweat glands

5. Decrease activity of digestive and urinary glands

6. Release epinephrine and norepinephrie (adrenaline)

1. Preganglionic neurons (located between T1-L2 on spinal cord)

2. Two types of ganglia near vertebral column

1. Sympathetic chain ganglia-aka paravertebral/lateral ganglia--lateral to to vertebral column on both sides

2. Collateral ganglia-aka prevertebral ganglia, anterior to the vertebral column

*Adrenal Medulla-direct connection to stimulate adrenal gland

Preganglionic fibers=short

Postganglionic fibers=long

ACh

Acetylcholine

1. Constriction of the pupils to restrict the amount of light entering the eyes

2. Secretion by digestive glands

3. Secretion of hormones that promote nutrient absorption by peripheral cells

4. Increased smooth muscle activity along digestive tract

5. Stimulation and coordination of defecation

6. Contraction of the urinary bladder during urination

7. Constriction of respiratory passageways

8. Reduction in heart rate and force of contraction

9. Sexual arousal and stimulation of sexual glands

Long: pass through spinal cord

Short: bypass spinal cord and go straight to the ganglionic neuron

-disease of the nervous system where communication between the brain and the body is disrupted

-Myelin around nerves is destroyed by T-cells (autoimmune disease)

-Initial symptom is often vision problems

-Most experience muscle weakness balance/coordination issues, abnormal sensory feelings ie numbness

-Worst case is partial or complete paralysis

*No cure, but medications can help to control symptoms

Blood flow

-interruptions

-oxygen deprivation

-glucose

-Interruption of blood flow for 1-2 minutes impairs neuron function

-total oxygen deprivation for 4 min causes permanent injury

-brain must have continuous supply of glucose

-glucose deprivation may produce mental confusion, dizziness, convulsions and unconsciousness

-protects brain cells from harmful pathogens-selective barrier

-injury due to trauma, inflammation or toxins causes a breakdown of the bbb.

-BBB may also prevent entry of drugs that could be used as therapy for cancer

-protective layers of the brain-->provide physical stability and shock absorption

-Continues around brain and spinal cord-->dura mater, arachnoid mater, pia mater

clear, colorless liquid that protects the brain and spinal cord against chemical and physical injuries

-contains glucose, proteins, and ions

-mechanical protection: floats brain and softens impact

-chemical protection: optimal ionic concentrations for action potentions

-Circulation: nutrients and waste products to and from bloodstream

-4 CSF filled cavities within the brain

-lateral ventricles: in each hemisphere of the cerebrum (separated by the interventricular foramen)

-third ventricle: narrow cavity along the midline superior to the hypothalamus and between the right and left halves of the thalamus

-fourth ventricle: between brain stem and cerebellum

1. Choroid plexus

2. Lateral ventricles

3. Interventricular foramen

4. Third ventricle

5. Cerebral aqueduct

6. Fourth ventricle

7. Central canal

8. Subarachnoid space

9. Around spinal cord

10. Around brain

11. Arachnoid villi

12. Blood via dural sinus

-Reabsorbed through arachnoid villi

-20mL/hour reabsorption rate (same as production rate)

Blockage of drainage of CSF (tumor, inflammation) while production still occurs causes increased pressure called hydrocephalus

-in newborn, fontanels allow pressure to expand skull-damages brain tissue

*Neurosurgeon implants a drain, which reroutes CSF to the veins in neck or abdomen

Components of the peripheral nervous system that connect to the brain

-12 pairs

-Use roman numerals

-attaches to the brain near the sensory or motor nuclei

I. Olfactory nerve-special sensory-smell

II. Optic nerve-special sensory-vision

III. Oculomotor nerve-motor-eye movements

IV. Trochlear nerve- motor-eye movements

V. Trigeminal nerve-sensory and motor of face-mastication

VI. Abducens nerve-motor-eye movement

VII. Facial nerve-sensory (taste), somatic motor-muscles of facial expression, visceral motor-lacrimal gland, nasal mucous gland, salivary gland

VIII. Vestibulocochlear nerve-special sensory-balance, equilibrium, hearing

IX. Glossopharyngeal nerve-sensory nuclei of medulla oblongata; somatic motor-swallowing muscles; visceral motor-parotid salivary gland

X. Vagus nerve-visceral sensory-from pharynx, auricle, external acoustic meatus, diaphragm, visceral organs in thoracic and abdominopelvic cavities; somatic motor-muscles of palate and pharynx; visceral motor-respiratory, cardiovascular, and digestive organs in thoracic and abdominal cavities

XI. Accessory nerve- motor-innervates voluntary muscles of palate, pharynx and larynx; controls sternocleidomastoid and trapezius muscles

XII. Hypoglossal nerve-motor-tongue movements

Homeostatic Disorders

Cerebrovascular (stroke)

-most common brain disorder

-3rd leading cause of death (heart attack and cancer=1&2)

1. ischemic: most common-decreased blood supply

2. hemorrhagic-blood vessel in brain bursts

Dementia= loss of reasoning, ability to read, write, talk, eat, walk

-Affects 11% of population over age 65

-Great loss of neurons in specific regions; loss of neurons that release ACh

-Plaques of abnormal proteins deposited outside neurons (amyloid plaques)

-tangled protein filaments within neurons (neurofibrillary tangles)

-Years 1-2: rapid increase in size due to increase in size of neurons, growth of neuroglia, myelination and development of dendritic branches

-Early adulthood-death: brain weight declines, number of synaptic contacts declines, processing of info diminishes, conduction velocity decreases, voluntary motor movements slow down, reflexes slow down 

Functions of the brain

Telencephalon: Cerebrum

Frontal lobe: Primary motor cortex-conscious control of motor neurons and higher order thought

Occipital lobe: Primary visual cortex-conscious awareness of visual information

Parietal lobe: Primary sensory cortex-conscious perception of touch, pain, temp, taste

Temporal lobe: Primary auditory cortex; primary olfactory cortex-conscious awareness of smell and sound

Functions of the brain

Diencephalon: Thalamus

-Sensory "relay station"/"switchboard" for cerebral cortex;

-Primitive awareness of sensory information.

-Considered the gateway to the cerebral cortex because ANY communication to cerebral cortex MUST go through thalamus where info is edited

Functions of the brain

Diencephalon: Hypothalamus

-Main control center for the ANS-regulates heartrate, blood pressure, digestive movement, body temp, salivary and sweat glands, hunger/thirst

-Center of emotions-rage, fear, pleasure, sex drive

-sleep/wake cycles

-Endocrine control

Functions of the brain

Mesencephalon: Cerebral peduncles

-Little feet of the cerebrum

-contain pyramidal (corticospinal) tracts descending from the cortex towards the spinal cord

Functions of the brain

Mesencephalon: Corpora quadrigemina

-"quadruplets"

-involved in visual reflexes (tracing of eyes on a moving object)

-involved in auditory reflex (startle reflex)

Functions of the brain

Metencephalon: Pons

-Bridge between cerebral cortex and cerebellum

-Coordination and voluntary movement

-respiratory centers to regulate inhalation/exhalation

Functions of the brain

Metencephalon: Cerebellum

-RECEIVES INFO ABOUT: equillibrium, current movement of body, motor commands from cerebral cortex

-Allows cerebellum to smooth and coordinate body movements and mantain posture/equillibrium

Functions of the brain

Myelencephalon: Medulla oblongata

-Pathway for pyramidal tract-sensory relay

-Subconscious movement for equillibrium

-Visceral centers for autonomic functions (adjusts force/HR, BP control, breathing rate, vomiting, hiccuping, swallowing, sneezing, coughing

-Work in conjunction w/hypothalamus

-Spinal cord and brain

-have functional independence

-spinal cord integrates and processes info

-processes reflexes

-site for integration of external and internal stimuli that arise locally or are triggered by nerve impulses from the periphery and brain

-Conduction pathway for sensory and motor nerve impulses

Meninges

-inflammation

-Clinical applications

-Inflammation=meningitis

-removal of CSF from subarachnoid space=spinal tap

-Shaped like the letter H

-Surrounded by white matter

-Gray matter consists of cell bodies of neurons and neuroglia and unmyelinated axons and dendrites of association and motor neurons

-divided into horns

-White matter consists of bundles of myelinated axons of motor and sensory neurons

-divided into RT and LT sides by anterior median fissure and posterior median sulcus

-Divided into columns

31 pairs numbered and named according to the region and level of the spinal cord from which they emerge

-8 pairs cervical nerves

-12 pairs thoracic nerves

-5 pairs lumbar nerves

-5 pairs sacral nerves

-1 pair coccygeal nerves

Path of communication between spinal cord and most of the body

1. Neuritis

2. Shingles

3. Poliomyelitis (Polio)

-Inflammation of nerves

-caused by injury, vitamin deficiency or poison

-Infection of peripheral nerves by chicken pox virus

-causes pain, skin discoloration, line of skin blisters

-Superficial

-Viral infection causing motor neuron death and possible death from cardiac failure or respiratory arrest

-Internal

-specialized cell or cell process that monitors conditions in the body or external environment

-Stimulation directly or indirectly alters the production of action potentials in sensory neuron

-Temperature, pain, touch, pressure, vibration, proprioception

-Receptors through the body

-Sensations arrive at the primary sensory cortex in the parietal lobe

-Olfaction (smell), gustation (taste), equilibrium (balance), hearing and vision

-Specialized receptor cells that are structurally more comple than those of general senses

Special sense receptors

characteristic sensitivity

Lobe innervation

Temporal

Frontal

Parietal

Occipital

Temporal: Auditory, olfactory

Frontal: Motor, gustatory

Parietal: General sensory, gustatory

Occipital: Vision

-SMELL

-10-20 million chemoreceptors in mucous membrane on roof of nasal cavity

-4 molecules of gas can cause an action potential

-Sends sensory info to temporal lobe

-Sensory tracts that bypass the thalamus to cerebrum

1. Olfactory receptors

2. Olfactory nerve

3. Olfactory bulb/tract

4. Sensory cortex in temporal lobe

-Sensory info about chemicals dissolved in saliva

-Receptors in the tongue and throat

-approx 40 receptors grouped in single taste bud

-Taste buds located along sides of papillae

-innervated by CN 7, 9, 10

1. Sweet-simple carbs

2. Salt-Na+

3. Sour-H+ acid

4. Bitter-complex carbs

5. Water

6. Umami-glutamate

1. Taste buds (anterior 2/3 of tongue)

2. Facial nerve

3. Medulla oblongata

4. Thalamus

5. Cerebral cortex in parietal/frontal lobe

1. Taste buds-posterior 1/3 of tongue

2. Glossopharyngeal nerve

3. Medulla oblongata

4. Thalamus

5. Cerebral cortex in parietal/frontal lobe

1. Taste buds of pharynx

2. Vagus nerve

3. Medulla oblongata

4. Thalamus

5. Cerebral cortex in parietal/frontal lobe

1. External ear

2. Middle ear

3. Internal ear

1. Auricle directs sound waves towards tympanic membrane

2. Auditory canal-lined with hair and cerumious glands

3. External auditory canal-tube that extends to tympaninc membrane

4. Tympanic membrane

5. Vibrations of the tympanic membrane convert sound waves into mechanical movements

1. Transmits vibrations from the tympanic membrane to the inner ear

2. Ossicles located in air-filled space vibrate

3. Transfer vibrations from tympanic membrane to fluid-filled chambers within inner ear

-Malleus

-Incus

-Stapes

*amplify and strengthen vibrations

1. Auditory tube (Eustachian tube) connects ear to nasopharynx and adjusts pressure in middle ear

2. Passes through the temporal bone

3. Normally collapsed sealing off middle ear

4. Opens to allow middle ear pressure to equilibrate with atmospheric pressure during chewing, swallowing, yawning

*common site of infections in children due to close proximity to the nasopharynx

1. bony labyrinth (canals within temporal bone)

2. Membranous labyrinth (connect tissue in bony labyrinth)

3. Contains cochlea

4. Contains semicircular canals/vestibule (equilibrium)

5. Mechanoreceptors found in cochlea

6. Stapes vibrates and moves inner fluids (perilymph/endolymph) like water bed

7. Hair cells bend as sound waves move fluid and membranes in cochlear duct

-Mechanoreceptors in semicircular ducts/ampulla sense dynamic equilibrium (movement of head/body)

-Mechanoreceptors in vestibule sense static equilibrium (position of head/direction of gravity)

1. External ear

2. Tympanic membrane

3. Middle ear bones (ossicles)

4. Motion of perilymph in vestibular and tympanic ducts

5. Vibration of vestibular and basilar membranes

6. Motion of endolymph

7. Vibration of organ of corti

8. Tectorial membrane stimulates hair cells

9. Cochlear nerve stimulated

10. Vestibulocochlear nerve (CN VIII)

11. Thalamus

12. Cerebral cortex in temporal lobe

1. Hair cells in utricle, saccule, and ampullae of semicircular canals/vestibule

2. Vestibular nerve

3.Vestibulocochlear nerve

4. Medulla oblongata

5. Cerebellum

Vision

Photoreceptors

Cones-detect color

rods-detect light/dark

1. Fibrous tunic

2. Vascular tunic

3. Nervous tunic

-Sclera: whites of the eyes

-Cornea: focus light (no blood vessels)

-Choroid: contains blood vessels

-Cillary body: muscle that suspends/moves lens

-Iris: pigment

-Lens: clear/flexible

-made of nervous tissue

-contains photoreceptors

-Fovea: concentration of cones at back of eye, site of sharpest vision

-Optic disc: "blind spot" where the optic nerve exits, no photoreceptors

Cones: 6 mil in posterior region of retina

-Detects 3 colors-red, blue, green

-high acuity

-Functions in bright light

Rods: 125 mil at periphery of retina

-Black and white vision

-low acuity

-function at low levels of light

Spinal nerve innervations

Cervical plexus

Spinal nerve innervations

Brachial plexus

1.

2.

Axillary nerve

-Deltoid

-teres minor

Musculocutaneous nerve

-coracobrachialis

-brachialis

-biceps brachii

Spinal nerve innervations

Brachial plexus

1.

2.

3.

Median nerve

-Pronator teres

-Flexor carpi radialis

-palmaris longus

-only nerve pass carpal tunnel

-hand of benediction

Ulnar nerve

-Flexor carpi ulnaris

-many hand muscles

-funny bone-most unprotected

Radial nerve

-Triceps

-brachioradialis

-extensor carpi radialis longus/brevis

-Extensor forearm muscles

Spinal Nerve Innervations

Thoracic nerve

Spinal Nerve Innervations

Lumbar Plexus

1.

2.

3.

1. Obturator nerve

-Abductor magnus

-abductor longus

-gracilis

2. Femoral nerve

-sartorius

-quadriceps

3. Saphenous nerve

-sensory of medial lower leg just distal to the knee down to the medial malleolus

Spinal Nerve Innervations

Sacral plexus

1.

2.

1. Gluteal nerve

-Superior: gluteus medius/minimus, tensor fasciae latae

-Inferior: Gluteus maximus

2. Sciatic nerve

-Biceps femoris

-Semitendinosus

-Semimembranosus

-Muscles of lower leg and foot

Spinal Nerve Innervations

Sacral plexus

3.

4.

3. Tibial nerve

-Gastrocnemius

-Tibialis posterior

4. Fibular nerve

-Tibialis anterior

-Extensor hallicus longus

-Fibularis longus/brevis

1. Motor cortex of cerebrum

2. Internal capsule

3. Mesencephalon

4. Pons

5. Medulla oblongata

6. Anterior horn (synapse)

7. Anterior root

*8. Exit appropriate ramus (ventral/dorsal)

*9. Appropriate plexus

*10. Appropriate spinal nerve(s)

*11. Muscle (synapse)

*1. Specific receptor

*2. Appropriate spinal nerve(s)

*3. Appropriate plexus

*4. Enters appropriate ramus (ventral/dorsal)

5. Dorsal root ganglion

6. Dorsal root

7. Dorsal horn (synapse)

8. Thalamus (synapse)

9. Internal capsule

*10. Appropriate sensory cortex (cerebrum)