Anatomy and Physiology Nervous System

functions of the nervous system

control center for all body activities, responds and adapts to changed that occur both inside and outside the body, and three overlapping functions

what are the three overlapping functions

sensory input, integration, motor output

sensory input

info gathered by sensory receptors about internal and external changes

integration

processing and interpretation of sensory input

motor output

activation of effector organs (muscles and glands) produces a response

the two principle parts of the nervous system

Central Nervous System (CNS) and Peripheral Nervous System (PNS)

central nervous system

brain and spinal chord of dorsal body cavity; integration and control center that interprets sensory input and dictates motor output

peripheral nervous system

the portion of nervous system outside CNS that consists mainly of nerves that extend from brain and spinal chord (spinal and cranial nerves)

nerves

connect nervous system with other systems (composed of 2 cells); visible bundles of axons and dendrites that extend from the brain and spinal chord to all other parts of the body

the 2 cells of nerves

neurons and neuroglia

neurons

nerve cells that send and receive signals; conduct impulses; has extreme longevity, amitotic (doesn't divide), high metabolic rate which requires continuous supply of oxygen and glucose; all neurons have cell body and one or more processes

neuroglia

supporting cells that separate and protect neurons, provide framework, act as phagocytes, regulate composition of interstitial fluid (AKA glial cells)

4 main neuroglia CNS neurons

astrocytes, microglial cells, ependymal cells, oligodendrocytes

astrocytes

most abundant and versatile glial cells; they have delicate branching structure; function in connecting capillaries to neurons

microglial

small ovoid cells with long thorny processes; touch neuron cells and monitor health; can turn into a special type of macrophage cell to phagocytize microorganisms or debris

ependymal cells

line the central cavities of the brain and spinal cord

oligodendrocytes

branching structure with fewer processes; forms myelin sheaths around CNS fibers which are insulating covers

3 things contained in neuron

cell body with nucleus, dendrites, axon

dendrites

highly branched fibers that receive messages from other neurons

axon

long fibers that send messages to target cell

synapse

connects functional neurons through junctions that mediate information transfer

Electrical synapse

(less common but abundant in embryonic tissue) gap junctions electrically couple neurons together and allow synchronized activities of all interconnected neurons

steps of info transfer across chemical synapse

action potential arrives at axon terminal of presynaptic neuron causing voltage gated Ca channels to open (AP clauses depolarization by allowing influx of Na); influx of Ca causes release of neurotransmitter from synaptic vesicles (via exocytosis); neurotransmitter diffuses across synaptic cleft and binds to receptor proteins on postsynaptic membrane, which causes ion channels to open and causes graded potential; neurotransmitters are either taken up by astrocytes or presynaptic terminals or diffuse away

acetylcholine

first identifies; functions at neuromuscular junctions

biogenic amines

dopamine, epinephrine, norepinephrine; emotional behavior and biological clock roles

amino acids

GABA

cephalization

evolutionary development of rostral portion of CNS; resulted in increased number of neurons; highest level reached in human brain

gray matter

short nonmyelinated neurons and cell bodies

white matter

myelinated and nonmyelinated axons

basic pattern found in CNS

central cavity surrounding by gray matter, with white matter external to gray matter

ventricles

fluid filled chambers that are continuous to one another and to central canal of spinal cord; filled with cerebrospinal fluid and lined with ependymal cells

paired lateral ventricles

large, C

third ventricle

lies in diencephalon; continuous with central canal of spinal cord; this is connected to the 4th ventricle via cerebral aqueduct; continuous with central Canal of spinal cord

the three openings that connect 4th ventricle to subarachnoid space that surrounds the brain

paired lateral apertures in side walls and median aperture in roof

3 surface markings

gyri, sulci, fissures

gyri

ridges

sulci

shallow grooves

fissures

deep grooves

longitudinal fissures

separated the two hemispheres

transverse cerebral fissure

separates cerebrum and cerebellum

5 lobes and what are they divided by

frontal, parietal, occipital, temporal, limbic; divided by sulci

what are the 3 major sulci that divide lobes

central sulcus, postcentral gyrus, and lateral sulcus

central sulcus

seperates pre central gyrus of frontal lobe and post central gyrus of parietal lobe

postcentral gyrus

of parietal lobe

lateral sulcus

outlines the temporal lobes

cerebral cortex

executive site of brain; site of conscious mind: awareness, sensory perception, voluntary motor initiation, communication, memory storage, understanding; thin superficial layer of gray matter

what are the 3 types of functional areas of the cerebral cortex?

motor areas, sensory area, association area

motor areas of cerebral cortex

control voluntary movement; located in frontal lobe; contains: primary motor cortex in pre central gyrus, premotor cortex anterior to pre central gyrus, brooks area anterior to inferior premotor area, and frontal eye fields within and anterior to premotor cortex

sensory areas of cerebral cortex

conscious awareness of sensation; occur in parietal, insular, temporal, and occipital lobes

visual areas of cerebral cortex

primary visual striate and visual association area

primary visual (striate

cortex located on extreme posterior tip of occipital lobe and receives visual info from retinas

visual association area

surrounds primary visual cortex that uses past visual experiences to interpret visual stimuli and complex processing involves entire posterior half of cerebral hemispheres

auditory areas of cerebral cortex

primary auditory cortex and auditory association area

primary auditory cortex

superior margin of temporal lobes that interprets info from inner ear as pitch loudness and location

auditory association area

located posterior to primary auditory cortex that stores memories of sounds and permits perception of sound stimulus

vestibular cortex of cerebral cortex

posterior part of insulation and adjacent parietal cortex that's responsible for conscious awareness of balance (position of head in space)

primary olfactory cortex of cerebral cortex

medial aspect of temporal lobes, part of primitive rhinencephalon along with olfactory bulbs and tracts involved in conscious awareness of odors

gustatory cortex of cerebral cortex

in insula eep to temporal lobe involved in perception of taste

visceral sensory area of cerebral cortex

posterior to gustatory cortex conscious visceral sensations such as upset stomach or full bladder

cerebellum

connected to brainstem; center for body movement and balance and contains the arbor vitae

hypothalamus

controls autonomic nervous system. center for emotional response and behavior, body temp, food intake, water balance and thirst, sleep

brainstem

most primitive part of brain and controls basics: breathing, heart rate, swallowing, reflexes, sweating, blood pressure, sleep, and balance

brainstem components

pons and medula oblongata

the medulla oblongata

control center for vital involuntary reflexes: vommiting, swallowing, sneezing, coughing, and regulation of cardiovascular and respiratory activity

pons

main function is to connect cerebellum to rest of brain

association areas of cerebral cortex

integrate diverse information

the hemispheres of the cerebral cortex

concerned with contralateral side of body

what can only occur in one hemisphere of the cerebral cortex; what involves entire cortex

lateralization (specialization) of cortical function; conscious behavior

cranial nerves

connect to brain

spinal nerves

attach to spinal cord

sensory nerves

carry messages from body to brain (pain, pressure, temperature)

motor nerves

carry messages from brain to body to respond

2 divisions of the PNS

afferent divisions and efferent divisions

afferent division

sensory neurons that brings sensory information to the CNS from receptors in peripheral tissues and organs from PNS

efferent division

motor neurons that carry motor commands from the CNS to the PNS muscles, glads, and adipose tissues

effectors

target organs that "do something"

2 divisions of the Efferent PNS

somatic and autonomic

somatic nervous system (SNS)

control skeletal muscle

autonomic nervous system (ANS)

controls smooth muscle, adipose tissue, and glandular activity

two types of ANS

sympathetic and parasympathetic

sympathetic

prepares body for heightened levels of somatic activity (fight or flight and stimulating effect)

parasympathetic

stimulates visceral activity (rest and digest, conserves energy and promotes digestion)