UNIT 3 Anatomy

Central Nervous System

brain and spinal cord

Peripheral nervous system

cranial nerves, spinal nerves, and ganglia

Sensory (afferent) NS

senses, somatic sensory and visceral sensory

Afferent

recieves sensory info from receptors in the PNS and transmit it to the CNS

Somatic sensory

voluntary, touch, pain, and pressure

Visceral sensory

involuntary, impulses from viscera, blood vessels, not consciously perceived homeostasis

Motor (efferent) NS

to make movement, somatic motor and autonomic motor

Efferent

send impulses from CNS to muscles and glands

Somatic motor

voluntary, impulses from CNS cause contraction of skeletal muscle

Autonomic motor

involuntary, impulse from CNS cause contraction of smooth and cardiac muscle

Dendrite

receive nerve impulses and carry them to the cell body

Cell body

summation to signal

Axon (nerve fiber)

transmits nerve impulses away from cell body and to other cells

Axon hillock

region where body is connected to the axon

Axon terminal/ synaptic end bulb

the swollen, bulb-like structure at the very end of an axon branch that converts electrical nerve impulses into chemical signals

Multipolar

many dendrites and one axon; most common (interneurons and motor)

Bipolar

two processes, one dendrite and one axon, rare (olfactory receptors), sensory

Unipolar

single, short process that branches like a T, sensory

Interneurons

facilitate communication between sensory and motor neurons; only CNS

Astrocyte

most abundant, CNS, maintain blood-brain barrier via regulation of blood flow, regulate tissue fluid composition, form structural network

Oligodendrocyte

CNS, wrap around axon like electrical tape wrapped around wire, produce myelin, insulator of electrical activity

Microglia

small cells that are motile, wander through CNS and phagocytes

Ependymal cell

CNS, ciliated cuboidal epithelial cells that line ventricles of the brain and the central canal of spinal cord, form the choroid plexus with capillaries and produces CSF

Schwann cells (neurolemmocyte)

PNS, wrap around axons like oligodendrocytes, produce myelin= insulator and speed up electrical

Satellite cell

flattened cells around neuronal cell bodies in PNS ganglion

Cells that make myelin sheath

Nuerolemmocyte- PNS

Oligodendrocytes- CNS

Process of myelination

forming a multi-layered lipid-protein protective membrane called a myelin sheath around a neuron's axon to speed up electrical signal transmission

Nodes of Ranvier= Neurofibril nodes

Between adjacent insulating cells (neurolemmocytes or oligodendrocytes) are spaces called neurofibril nodes

What is their role in the conduction of a nervous signal?

Electrical signal “jumps” from node to node so it travels much more quickly down axon=saltatory

Nerve fibers

Both, axons of neurons, can be myelinated or unmyelinated, speed transmission increases with: increased size of fiber-increased diameter

Nerve

bundles of afferent and efferent fibers (axons) in PNS, outside CNS, white mater

Tracts

bundles of afferent and efferent fibers (axons) within CNS, white mater

Ganglia

cell bodies in groups, PNS, gray mater

Gray mater

unmyelinated fibers and cell bodies

White mater

myelinated nerve fibers bundled together

Nuclei

masses of cell bodies and dendrites (CNS), gray mater

Action potential

electrical signals travel down the axon via action potentials

Action potential process

Rapid flow of ions across the cell membrane, once an action potential begins it triggers more down the axon until signal reaches the axon terminal (dominos)

Synapses

specialized junction between two cells through which a signal is passed

Types of presynaptic structures

Axondendritic and axonsomatic, chemical, electrical

Types of postsynaptic structures

Electrical, axondendritic, and axonsomatic

Electrical synapse

between gap junctions of tightly connected cells; directly transmit electrical signal from one cell to the next (cardiac and smooth muscle tissue)

Chemical synapse

electrical signal in presynaptic cell causes release of neurotransmitter (chemical) into synaptic cleft

List the basic steps of transmission via a chemical synapse

1. Presynaptic nerve impulses

2. Synaptic vesicles release neurotransmitter into synaptic cleft

3. Receptors in post-synaptic cell open ion channels

4. Electrical to chemical to electrical

Germ cell derivation of the nervous system

Ectoderm

The process by which nervous tissue structures form in the embryo is called

Neurulation

Explain how regeneration of nervous tissue can occur. Is this limited in either the CNS or PNS?

Nervous tissue regeneration happens differently depending on whether the damage is in the peripheral nervous system (PNS) or the central nervous system (CNS)

Meninges function

Cover, support, and protect the CNS

Dura mater (durable)

made up of dense fibrous CT layer around the brain, from dural sinuses that drain blood from brain

Dural septa

extend between hemispheres (falx cerebri) and elsewhere

Dural sinuses

layers that separate in certain areas , drain blood from brain

Arachnoid mater

middle, deep to dura mater, separate from it by subdural space, made of loose fibrous tissue with collagen and elastin-web-like appearance

Subarachnoid space

space below arachnoid mater, filled with CSF and large blood vessels

Pia mater

areolar CT, adheres tightly to the surface of the brain

Cerebrospinal fluid (CSF)

watery solution similar to blood plasma (derived from plasma), form liquid cushion, give buyoncy to CNS organs

Where, in relation to the meninges, is CSF found?

Subarachnoid space

Blood-brain barrier

selective barrier made of endothelial tight junctions of capillaries and astrocytes, allow nutrients to pass freely, keep some substances away from neurons

Lateral brain ventricle

a pair of large, C-shaped, fluid-filled cavities located within the cerebral hemispheres of the brain

Third brain ventricle

a narrow, slit-like cavity located along the midline of the brain's diencephalon, positioned between the left and right thalami

Fourth ventricle

a tent-shaped, fluid-filled cavity in the human brainstem that circulates cerebrospinal fluid (CSF) and protects the central nervous system

CSF formation

formed from blood by ependymal cells at choriod plexuses in brain ventricles, flows around the brain

Where is CSF resorbed into the blood stream?

Reabsorbed into circulation at arachnoid vili in dural sinuses

Superficial gray matter of the cerebrum is called the _____________________________. Its

functions include:

Cerebral cortex; sensory processing, high reasoning processing, memory and language

Gyri (gyrus)

a ridge or fold on the surface of the cerebral cortex of the brain

Sulci (sulcus)

shallow depressions or indentations on the surface of the human cerebral cortex.

Fissures

deep grooves or furrows in the surface of the cerebral cortex that divide the brain into distinct hemispheres and lobes.

Longitudinal fissure

divide cerebrum into R and L hemispheres

Central sulcus

a prominent groove in the cerebral cortex of the brain that separates the frontal lobe from the parietal lobe.

Parieto-occipita sulcus

separates parietal and occipital lobes

Lateral sulcus

most prominent deep groove on the lateral surface of each cerebral hemisphere of the human brain.

Frontal lobe

voluntary motor functions, concentration, verbal communication, decision making, planning and personality

Parietal lobe

general sensory functions

Temporal lobe

hearing and smell

Occipital lobe

processing visual info, storing visual memories

Insula

deep to lateral sulcus, involved in emotional response, empathy and interpretation of taste

Left hemisphere

right skeletal muscle control, general sensation from right half of body, controlling and understanding speech, numeric and scientific skill

Right hemisphere

L skeletal muscle control, general sensation from Left half, creative artistic skill

Primary motor cortex

located in precentral gyrus of frontal lobe, control voluntary contraction of skeletal muscles, different parts of the body map to different areas of the motor cortex

Premotor area (somatic motor associated area)

anterior to primary motor area, involved in complex and repetitive (learned) motor control, sensory-guided movement, initiation of movement

Frontal eye field area

anterior to premotor area, controls and regulates eye movement, keeps gaze steady on a moving object

Primary somatosensory cortex

located postcentral gyrus of parietal lobe, interpret somatic sensations of touch, pressure, pain, temp across the body

Somatosensory association area

is a region of the cerebral cortex that interprets and integrates touch, pressure, temperature, and pain information received from the primary somatosensory cortex

Primary visual area

receive processes visual info

Visual associated area

integrates info from primary visual cortex to make interpretations (recognize specific objects)

Primary auditory area

receives and processes auditory info, interpretation of pitch and rhythm

Auditory association area

a region of the cerebral cortex adjacent to the primary auditory cortex that interprets and gives meaning to sounds, speech, and music

Primary olfactory area

temporal lobe, receives info from olfactory bulb for sense of smell, does not have to process through thalamus

Primary gustatory area

insula, processes sensation of taste

Prefrontal cortex

anterior frontal lobe, involved with intellect, cognition, recall, and personality, necessary for judgement, reasoning, persistence, and conscience

Motor speech area (Broca’s area)

frontal lobe of left hemisphere, controls muscular movement involved in speech production

Language association area (Wernicke’s Area)

between parietal and temporal lobes in left hemisphere, basic speech comprehension, and associated with problems of speech input

Common integrative area, Gnostic area

parts of parietal, occipital, and temporal lobes, integrates all sensory, auditory, olfactory, and visual info

White mater of cerebrum: Association fibers

connect regions of cerebral cortex within the same hemisphere

White mater of cerebrum: Commissural tract

connect right and left hemispheres (corpus callosum)

White mater of cerebrum: Projection fibers

connect cerebrum to rest of brain and spinal cord