PSIO 241 CH 5

central nervous system (CNS)

including the brain and spinal cord

peripheral nervous system (PNS)

including the peripheral nerves connecting target cells/organs to the CNS

enteric nervous system

the nerve network of the digestive tract

somatic

carries sensory information from skin, skeletal muscles

visceral

carries sensory information from smooth muscle, glands and organs – aka autonomic

afferent (input) divisions: sensory

* somatic
* visceral

shares information about an organ into the system

efferent (output) divisions: motor

* somatic nervous system
* autonomic nervous system

somatic nervous system

motor neurons that supply skeletal muscles

autonomic nervous system

motor neurons that innervate smooth muscle, cardiac muscle, and glands (involuntary)

autonomic divisions

* sympathetic
* parasympathetic

sympathetic nervous system

fight or flight response

parasympathetic nervous system

resting/digesting

astrocytes

* physical support neurons in proper spatial (3d space) relationships
* induce formation of blood-brain barrier
* take up excess K+ to help maintain proper brain ECF ion concentration and normal neural excitability

oligodendrocytes

* form myelin sheaths in CNS

\- get attacked in MS

microglia

play a role in defense of brain as phagocytic scavengers

ependymal cells

contribute to formation of cerebrospinal fluid

meninges

_ covers CNS

dura mater

tough outer coat

arachnoid matter

blood vessels

subarachnoid space

filled with cerebral spinal fluid (blood)

pia mater

on brain surface

blood-brain barrier

_ limits access of blood-borne material into brain tissue

cerebrospinal fluid (CSF)

cushioning fluid that surrounds brain and spinal chord (CNS)

\- is produced inside ventricles in the brain and flows out into the subarachnoid space

ventricles and CSF

• Serves as a shock-absorber to prevent brain from hitting skull.

• **Exchange of materials** between neural cells and interstitial fluid surrounding brain.

• Constant production and flow out of CNS and into venous system; **carries wastes out of CNS**.

blood and oxygen supply

• Brain depends on a **constant blood supply.**

• Unlike most tissues **the brain cannot produce ATP without O2**.

• Brain normally **uses** only glucose but **does not store any**.

Under resting conditions the brain uses **20% of the O2** and 5**0% of the glucose** **consumed in the body**

more basic the function

the lower the part of the brain the _

cerebrum

• makes up about 80% of total brain weight.

• Largest unit in the brain

Longitudinal fissure

deep groove that separates cerebrum into right and left **cerebral hemispheres**

* each hemisphere divided into lobes

gyrus

thick fold

sulcus

shallow grove

cerebral cortex

* Outer surface of each hemisphere composed of gray matter and is the complex integrating area of the brain
* caps core of white matter
* organized into __6 well defined layers__

gray matter

* primarily neuronal cell bodies, dendrites, and glial cells
* integration of neural input and ignition of neural output

white matter

* contains all axons, surrounded in myelin
* consists of bundles of nerve fibers that interconnect brain areas

occipital lobe

houses the visual cortex

temporal lobe

houses the auditory cortex

parietal lobe

responsible for reception and perception of somatosensory input - somatic

frontal lobe

responsible for voluntary motor movement

somatosensory cortex

Site for processing and perception of both somesthetic (sensation from surface) and proprioceptive (awareness of position) input

• Located in each parietal lobe as the **post-central gyrus.**

somesthetic sensations

from the surface of the body (touch, pressure, heat, cold, and pain)

proprioception

awareness of body position

opposite

• The somatosensory cortex receives input from the **_** side of the body.

• Regions of the somatosensory cortex receives input from a **specific areas of the body**.

sensory homunculus

the distribution map

* the size of each body part in the homunculus is **proportional** to the level of sensory perception associated each body part

primary motor cortex

• Located in the frontal lobe as the **pre-central gyrus.**

• Controls **voluntary movement** produced by skeletal muscles

• Sends information to the**ventral portions of the spinal cord** to **activate motor neurons**

motor cortex

_ on each side of the brain primarily controls muscles on the opposite side of the body

larger

Body parts needing fine control of movement occupy _ area of motor homunculus