Central Nervous System

(CNS)

• Brain
• Spinal cord

Peripheral Nervous System

(PNS)

• Neural and glial tissue outside of the brain and spinal cord
  • nerves
  • ganglia

• sensory - detects information about the body and world around it
• input
  • Somatic senses - skin, muscles, joints
  • Special senses - vision, hearing, smell, taste, equilibrium
  • Visceral senses - fullness, blood pressure, blood pH, nausea

• Performs computations
  • Simple ones - reflexes
  • Complex ones - integration of sensory information, planning, emotions, and thinking
  • Stores memories

• Motor
• Sends signals to effectors organs to carry out decisions - cardiac muscle, smooth muscle, skeletal muscle, endocrine glands, exocrine glands
  • Somatic - skeletal muscle
  • Autonomic - sympathetic and parasympathetic control of cardiac muscle, smooth muscle and glands

• Mostly neuronal cell bodies, their dendrites, and axons that synapse on those dendrites

• Mostly myelinated axons
• High fat content of glial cells makes them appear white

• mainly on the outside
• islands of gray matter deeper in the white matte called nuclei

• Spinal cord
  • runs up and down on the outside
  • gray matter on the inside

• a group of neuronal cell bodies in the CNS - but outside the cortex

• a group of neuronal cell bodies in the PNS

• a group of axons running within the CNS

• a group of axons, and associated supporting structures in the PNS

• Cerebrum
• Diencephalon

• Divided into left and right cerebral hemispheres, connected to each other by white matter - three components
  • cerbral cortex
  • subcortical nuclei
  • white matter

• Organized into lobes
  • Frontal - logic, planning, personality
  • Parietal - processing of somatic sensory informaiton
  • Temporal - auditory and olfactory
  • Occipital - task of processing visual information
  • Isula - emotional functions

• Logic, planning, personality, some language function, initiates voluntry movements
  • the left frontal lobe initiates voluntary movements that control the right side of the body and vice versa

• Processing of somatic sensory information
• Some advanced visual processing, like recognizing shapes
• Some language functions
  • most sensory information that comes into the cortex, also crosses from left to right and vice versa
  • somatic sensory information

• auditory and olfactory information
• some language
• also includes the amygdala and hippocamus, which are important for both long-term and short-term memory

• this lobe is completely dedicated to the difficult task of processing visual information

• some emotional functions

• include the caudate nucleus, putamen, globus pallidus, substantia nigra
• crucial for many emotions
  • fear, sex drive, happiness, anger
• includes dopamine producing reward centers
  • involved in reward and addiction
• work with cerebellum to coordinate motions
• maintains activity in repetitive motions
  • walking
• involved in the process of learning

• Axons that interconnect cerebral areas, and connect cerbrum to brainstem, cerebellum, and spinal cord
  • different language areas of the cortex are interconnected through the white matter
  • corpus collosum is the large bundle of white matter interconnecting the two hemispheres

• thalamus
• hypothalamus

• located in the diencephalon
• synaptic relay station for sensory information on its way to the cerebral cortex (except smell)
  • somatic sensory information
  • visual sensory information
• involved in attention
  • information we are paying attention to is given priority over information we are ignoring
• interacts with the cortex in the attention process

• located in the diencephalon
• exerts its effects through neural pathways within the brain
  • neural pathways that activate parts of ANS
  • and through endocrine actions
• Thirst
  • monitors the osmolarity of the ECF releasing ADH when the osmolarity of the ECF is to high
• Hunger
  • integrates neural & hormonal signals to generate the feeling of hunger

• blood pressure regulation
• body temperature
• blood pH regulation

• Emotions
  • works together with some subcortical nuclei
    • stress, anger, and sex drive
• Endocrine regulation
  • major role and major link between the nervous and endocrine systems

• Cardiovascular-Digestive-Respiratory
  • initiates "fight or flight" responses, to give changes in blood flow patterns, increasing heart rate, and increasing breathing rate
  • decreases heart rate when relaxing or meditating
  • increases heart rate when sexually excited

• Major link between the nervous and endocrine systems
• helps regulate many processes
  • childbirth
  • metabolism
  • stress responses
  • growth during development

• Midbrain
• Pons
• Medulla oblongata

• Many nuclei, with diverse functions
• These nuclei are surrounded by tracts of white matter connecting brain and spinal cord
• Processing centers for 10 of the 12 pairs of cranial nerves (part of the PNS)
• Many autonomic control centers often working in conjunction with the hypothalamus
• Respiratory rate and force of breathing
• Helps control sleep/wake cycles, arousal, attentiveness in brain

• Heart rate and force of heartbeat
• Digestive Rate
• Autonomic reflexes, vomiting, swallowing, contractions and dilation of smooth muscle in respiratory bronchioles
• receives input from the hypothalamus and cortex
• receives afferent input form the PNS

• coordinates motor movements
  • plans and initiates movements
• monitors the progress of those movements
  • afferent components
• tells the frontal lobe when a correction is needed to ensure the movement achieves its goal
  • via the thalamus
  • efferent components

Spinal Cord

Anatomy

• Continuous with brainstem
• Enclosed and protected by bones of the vertebral column
• Only 1.4 cm in diameter at it widest
• Gives rise to 31 pairs of spinal nerves (part of PNS)
• In cross-sectin there is abutterfly-shaped, internal region of gray matter, and an external region of white matter

Spinal Cord

Functions

• Sensory
  • On the posterior side of gray matter are secondary sensory neurons that receive input from primary sensory neurons
  • connect to motor neurons in the spinal cord to mediate reflexes
  • carry the sensory information up to the brain
• Motor
  • On the anterior side of gray matter are secondary motor neurons with axons that travel in the spinal nerves which control effectors

Spinal Cord

White matter

• white matter contains tracts of axons, relaying sensory information up to the brain and motor information down from the brain

• Primary somatoasensory receptor in skin
• Relay to secondary sensory neuron in posterior portion of spinal gray matter
• Relay in thalamus
• Main information processing in parietal lobe
  • ex:  feeling of pain

• Planning of movement in frontal lobe
• Initiation of movement by primary motor neuron in frontal lobe
• Relay to secondary motor neuron in anterior portion of spinal gray matter
• Secondary motor neuron innervates skeletal muscle, to cause contraction
• Proprioception, cerebellum, sub-cortical nuclei and thalamus all participate in adjustments to the movement

• a cyclically occurring state of decreased motor activity and perception

• Allows body to rest and recover
• Allows body to conserve energy
• Allows brain to dream
  • helps the brain practice and refine adaptive behaviors
  • helps consolidate memories
• Allows immune system time to work
  • animals deprived of sleep are more prone to infection

• induced by the forebrain
  • actives adenosine, a neurotransmitter involved inducing sleep
  • Caffeine blocks adensine
• waking up is stimulated by the ascending reticular activating system (ARAS)
  • this is a "diffuse network of nuclei" of the brainstem

• Slow wave sleep (non-REM sleep)
  • dreaming is sparse
  • dreams are more logical, less emotional
  • muscle tone present, but diminished compared to awake state
• REM
  • dreams more elaborate, vivid, and intense
  • dreams more bizarre, often tell a story
  • nightmares more frequent
  • increase in brain activity in most places
  • decease in activity in some parts of brainstem
  • no muscle tone in postural muscles
  • facial muscles, eye muscles, and muscles of distal limbs frequently twitch

• when you fall asleep, you go into SWS
• during the night, people go through about 4 cycles of SWS to REM sleep and back at 90 minute intervals

• controlled by the hypothalamus
• stimulated by the hormone ghrelin secreted by the stomach and pancreas
• sight of something delicious sends neural signals to the hypothalamus from the cortex

• stretching of the gastrointestinal tract
  • detected by mechanoreceptors
• nutrients in the duodenum
  • detected by chemoreceptors
• the hormone insulin
  • released by the pancreas
• the hormone CCK (cholecystokinin)
  • released by the small intestine
• the hormone leptin
  • secreted by adipose cells, release after meals

• most important for long-term regulation of nutrient intake
• when intake exceeds demand, we deposit fat in adipose tissue, which leads to leptin secretion, which suppresses appetitie and increases our metabolic rate

• in temporal and parietal lobes, usually in left hemisphere
  • responsible for comprehension of language
    • understanding written, spoken or signed language

• in frontal lobe, usually in left hemisphere
  • responsible for construction of meaningful language, writing, speaking or signing with correct syntax

• acquisition of new information or skills

• making connections between two or more stimuli
  • learning to associate pain with the image of a hot stove burner
  • learning to assoicate a tree with the delicious fruit that it makes

• becoming sensitized over time, due to repetition of a stimulus
  • increased positive or negative feelings
  • ex:  you might see someone cute walk by your house, and have a positive feeling about them.  If you keep seeing them walk by day after day your positive feeling might increase over time
• habituated leaning over time, due to repetition of a stimulus
  • decreased positive or negative feelings
  • ex:  you might see an amazing movie, and have a strong positive feeling about it, but if you see it 10 times, you might have a decreased positive feeling about it

• retention of information, skills, or thoughts

• memory of learned motor skills or behaviors
  • ex:  remembering how to ride a bike or play an instrument
• memories are consolidated, by the process of repetition
• stored in the cerebellum, subcortical nuclei, and pons

• memory of facts or experiences
  • ex:  remembering the names of the presidents
  • conscious awareness, as short-term memories
    • ex:  recalling a phone number between the time you read it and the time you dial the phone
• Stored in the frontal lobe
• The amygdala and hippocampus are involved in transferring delarative memories to long-term storage

• the capacity of the nervous system to strengthen existing synapses, and to build new synapses
• The patterns of synaptic connectivity represent memory traces that can be re-activated during memory recall
• The ability to learn and remember