ch. 7 | the nervous system

nervous system functions:

-info input

-info processing

-info output 

• central nervous system (CNS): composed of brain & spinal cord

-processes info/sensory data

-makes decisions/initiates response 

• meninges: 3 membranes covering the brain & spinal cord (superficial--> deep)

1. dura mater
2. arachnoid mater
3. pia mater 

• 4 ventricles:

1. left lateral
2. right lateral
3. third
4. fourth

spinal cord:

-gray matter is divided into horns: 

anterior horns: motor neurons  

posterior horns: sensory neurons

lateral horns: autonomic neurons 

-white matter: external part of spinal cord, myelinated axons of sensory/motor neurons

-nerve roots: connect spinal cord to PNS

ventral root: efferent, descending tracts, motor info

dorsal root: afferent, ascending tract, sensory info

-spinal nerve: where ventral & dorsal roots combine

-spinal cord does not extend through entire length of vertebrae

-thickest in cervical & lumbar regions (enlargements), thinnest at thorax

cranial nerves:

• cerebrospinal fluid (CSF): fluid found in the brain & spine; produced in choroid plexuses of ventricles of brain; acts as a cushioning 
• peripheral nervous system (PNS): consists of nervous tissue structures that lie outside the brain & spinal cord

-senses changes in environment

-sends info to CNS

-receives info from CNS

sensory (afferent) nervous system:

-somatosensory receptors

-special sense receptors

-autonomic sensory receptors 

motor (efferent) nervous system:

• somatic nervous system: voluntary, controls skeletal muscles, 1 motor neuron
• autonomic nervous system: involuntary, controls smooth/cardiac/glands, 2 motor neurons

       o sympathetic: fight or flight

-uses ACh as preganglionic neurotransmitter 

-epinephrine or norepinephrine as postganglionic neurotransmitter

-increases heart rate/blood pressure --> delivers oxygen & nutrients to working muscles

-increases rate of breathing --> bring more oxygen into body

-breaks down glycogen & releases glucose --> energy for working muscles

-inhibits digestion --> keeps blood from being diverted from muscles

       o parasympathetic: rest & repair/rest & digest

-uses ACh as pre/postganglionic neurotransmitter

-stimulation of digestive tract --> increased digestion

-vasoconstriction decreases blood flow --> shunts it toward digestive tract

-relaxes bladder & anal muscles --> increased urination & defecation

neurons:

-interneurons: extend for short distances, btwn afferent & efferent, found in gray matter

-ganglion: collection of nerve cell bodies found in PNS

• synapse: junction btwn 2 neurons 
• neurotransmitter: released into synaptic cleft in response to nerve impulse 

plexus: network of neurons formed from emerging branching spinal nerves from spinal cord

• cervical: distributes to diaphragm
• brachial: distributes to muscles of arm
• lumbar: distributes to femur/knee
• sacral: distributes to gluteus muscles, sciatic (runs down leg)