HSC4558: Exam 3

systems that make up the nervous system

-central nervous system

-peripheral nervous system

-autonomic nervous system

consists of the brain and spinal cord

central nervous system

consists of 31 pairs of spinals nerves and 12 pairs of cranial nerves

peripheral nervous system

consists of sympathetic and parasympathetic branches

autonomic nervous system

primary functions of the CNS

- receiving and processing sensory info

- creating appropriate responses to relay to muscles and glands

coordinates emotion, memory, cognition, and learning

CNS

support and protection of the CNS

• bony structures of the skull and vertebral column

  • protect from external injury

• Meninges

• Cerebrospinal fluid (CSF)

• Blood-brain barriers

  • provides internal protection

  • shield from harmful circulating substances

    • may interupt/block delivery of theraputic drugs

provides buuyancy and shock-absorbing capcity

• Meninges

• Cerebrospinal fluid (CSF)

cavities within the brain that are filled with CSF

ventricular system

membrane covering the brain and spinal cord

meninges

affix the brain to the skull so that the brain is suspended and supported

meninges

layers of meninges

• dura mater

• arachnoid mater

• pia mater

  • very thin, attached to the brain, follows every contour (sulcus and gyrus)

describe the dura mater layer of meninges

• two layers: periosteal & meningeal

• outermost layer; thick, tough, collagenous;

• protects soft brain tissue

describe the arachnoid mater layer of meninges

• middle layer; thin, delicate, semitransparent, web-like;

• potential space unless pathology present;

• CSF flows here (subarachnoid space)

potential space

space between two adjacent structures (when pathology present - movement present)

types of potential space

1. epidural (btw. dura & skull)

2. subdural (btw. dura & arachnoid)

describe the pia mater layer of the meninges

very thin, attached to the brain, follows every contour (sulcus and gyrus)

space that contains the CSF

subarachnoid space

communicates directly with the ventricular system

subarachnoid space

CSF is reabsorbed through

arachnoid villi: grapelike clusters of arachnoid that penetrate dural venous sinus

rate at which CSF is reabsorbed and produced

20 ml/hr

origin of CSF

choroid plexus

capillaries covered by ependymal cells

choroid plexus

choroid plexus contains

-2 lateral ventricles, one within each cerebral hemisphere

-roof of 3rd ventricle

-fourth ventricle

level of CSF in adults

150 ml

level of CSF produced and reabsorbed per day

500 ml/day

functions of the CSF

-Mechanical support

-Remove metabolic products from the brain

-Transport chemical messenger compounds

-Maintain chemical environment of the brain

glucose levels in the CSF will decrease due to

infection

protein levels in the CSF will increase due to

inflammation

RBC will increase in the CSF due to

trauma, subarachnoid hemorrhage

WBC increase in the CSF due to

infection (ex. meningitis)

Pressure of H2O will increase in the CSF due to

mass lesions

blood-brain barriers

joined by tight junctions

factors that affect permeability of BBB

- Inflammation

- Neovascularity

- Toxins

-Infants <6 months

four principal structures that divide the brain

-cerebrum

-diencephalon

-cerebellum

-brainstem

cerebrum contains

Cerebral cortex, basal ganglia, limbic cortex, and corpus callosum

diencephalon contains

thalamus and hypothalamus

brainstem contains

midbrain, pons, medulla oblongata

lobes of the cerebrum

1. frontal lobe

2. parietal lobe

3. temporal lobe

4. occipital lobe

contains the motor cortex, involved in complex thought, motivation, and morality

frontal lobe

contains the somatosensory cortex and the limbic area is involved in memory and emotion

parietal lobe

contains the auditory and vestibular centers and parts of the language center

temporal lobe

contains the visual cortex

occipital lobe

centrally located structure that processes and relays most of the signals traveling to and from the cortex and lower centers

thalamus

regulatory center for the ANS and along with the pituitary, produces and secretes hormones

hypothalamus

coordinates smooth movement and maintains posture and balance

cerebellum

critical for transmission of impulses between the brain and spinal cord

brainstem

contains vital centers for regulating respiratory and cardiovascular function (medulla and pons)

brainstem

mediates spinal reflexes involved in maintenance of posture, protective responses to pain, urination, and muscle tone

spinal cord

tracts of the spinal cord are

somatotopically organized so that innervation of a particular body region is connected to a specific region of the cerebral cortex

the spinal cord is protected by

spinal vertebrae and meninges

groups of cell bodies

ganglia (PNS)

the nerves of the PNS is supported and protected by

a sheath of connective tissue NOT by CSF or meninges

serves afferent sensory function and efferent motor function of the somatic and autonomic systems

PNS

cranial nerves of the PNS originate in

the brainstem

-except for CN I & II

CN I & II originate in the

diencephalon

coordinates motor, sensory, or mixed motor and sensory functions to specific areas of the body

cranial nerves

spinal nerves of the PNS

8 cervical

12 thoracic

5 lumbar

5 sacral

1 coccygeal pair

spinal nerves of the PNS merge into a large group called a

plexus

-except for T2-T12

segment of the body innervated by a spinal nerve is called

dermatome

composed of neurons in the CNS and PNS that mediate autonomic or involuntary functions

autonomic nervous system

has sensory afferents and motor efferents that primarily innervate visceral organs and blood vessels

ANS

neural responses in the ANS are communicated to the target organs by

the sympathetic and parasympathetic nervous system

the effect of the SNS and PSNS on target organs is nearly always

antagonistic

nervous system is composed of two principal cell types

neurons and glial cells

generate and transmit nerve impulses

neurons

provide supportive functions to neurons

glial cells

outnumber neurons 10:1

glial cells

three parts of a neuron

cell body, dendrites, axon

receive signals and transmit them to the cell body

dendrites

generates and conducts action potentials

axon

conduction of action potentials is faster in

large and myelinated axons

four types of neuroglia (glial cells)

oligodendrocytes, astrocytes, microglia, ependymal cells

form myelin sheath that wraps around nerve axons

oligodendrocytes

maintain integrity of the blood-brain barriers, regulate ionic balance of the interstitial fluid, and transfer nutrients from capillaries to neurons

astrocytes

provide phagocytic functions

microglia

produce. CSF and maintain CSF-brain barrier

ependymal cells

supporting cells of the PNS

Schwann cells: stimulate myelin production and maintenance

Satellite cells: provide physical support of neurons

neuronal communication is controlled by

membrane potentials

initiated when neurotransmitters bind to receptors on the dendrite and cell body and allow cations (especially sodium) to leak in

action potential

speed of the action potential is determined by

axonal diameter and myelination

chemical messengers released by neurons

neurotransmitters

propagate an electric impulse from one neuron to another

neurotransmitters

neurotransmitters are categorized according to

chemical structure

examples of neurotransmitters

acetylcholine, amines, amino acids, neuropeptides, purines, gases

create excitatory postsynaptic potentials (EPSPs)

excitatory neurotransmitters

example of EPSPs

Na, Ca influx

create inhibitory postsynaptic potentials (IPSPs)

inhibitory neurotransmitters

example of IPSPs

K, Cl efflux

determines whether an action potential will be initiated

summation of EPSPs and IPSPs at the axon hillock

sensory function is activated by

specialized dendritic processes, sensory receptors, at the ends of sensory afferents that project to the spinal cord

after sensory neurons in the cord are activated

signals are carried up the spinal cord to the brain

relays signals to various brain areas, including the somatosensory cortex in the parietal lobe

thalamus

motor function requires interaction among the

basal ganglia, cerebellum, and cortex

motor function is transmitted from

the primary motor cortex down the corticospinal tract

corticospinal tract primarily controls

distal muscles of the arms and legs

large proximal muscle groups and axial muscles are innervated by the

vestibulospinal, reticulospinal, and tectospinal tracts

occurs as direct result of the initial insult

primary brain injury

refers to progressive damage resulting from the body's physiologic response to the initial insult

secondary injury

critical factor in determining the neuronal cell fate after injury is

the degree of adenosine triphophosphate (ATP) depletion