Virginia Tech BMSP 2135 RAT #15

what are the 2 divisions of the nervous system?

CNS, PNS

what organs comprise the CNS?

brain, spinal cord

what organs comprise the PNS?

spinal nerves and their branches, cranial nerves

CNS: brain

- Enclosed completely by the skull

- Composed primarily of ___________ _________

- Consists of 100 billion neurons/nerve cells

- Lots of functions from the regulation of breathing and the processing of algebra to performing in the creative arts

nervous tissue

CNS: spinal cord

- Connects the brain with the peripheral NS and performs certain integrative functions

- Brain merges with the spinal cord at the __________ _______________

- Passes through the vertebral foramen of the 1st cervical vertebra and continues inferiorly to the 1st or 2nd lumbar vertebra

- Contains fewer cells than the brain (~100 million neurons)

- Enables the brain to communicate with most parts of the body below the head and neck

- Also able to carry out certain functions on its own

foramen magnum

PNS

- _____________ = most numerous organs of the NS

- Consist of bundles of axons, CT sheaths, and blood vessels

- Carry signals to and from the CNS

nerves

what are the 2 types of nerves?

cranial, spinal

cranial nerves

- originating from or traveling to the brain

- _____ pairs

12

spinal nerves

- originating from or traveling to the spinal cord

- _____ pairs

31

What are the three basic functional processes of the nervous system?

sensory functions, integrative functions, motor functions

basic functions of the NS

_____________ functions involve gathering information about the internal and external environments of the body

sensory

basic functions of the NS

________________ functions: analyze and interpret the detected sensory stimuli and determine an appropriate response

integrative

basic functions of the NS

integrative functions are performed entirely by the _______, mostly by the brain

CNS

basic functions of the NS

_____________ functions: the actions performed in response to integration

motor

basic functions of the NS

motor output is performed by the motor (efferent) division of the ________

PNS

Sensory input is gathered by the sensory (_____________) division of the PNS

afferent

sensory input

- carried from sensory receptors to the where? by cranial and spinal nerves of the PNS

- sensory stimuli are first detected by sensory receptors = specialized part of a neuron that detects changes in the internal and/or external environment

spinal cord and/or brain

what are the 2 ways to classify sensory information?

somatic, visceral

somatic sensory division

- consists of neurons that carry signals from skeletal muscles, bones, joints, and skin

- also includes sensory neurons that transmit signals from the organs of vision, hearing, taste, smell, and balance

- sometimes these particular neurons are referred to as the _____________ sensory division

special

visceral sensory division

consists of neurons that transmit signals from viscera (____________) such as the heart, lungs, stomach, intestines, kidneys, and urinary bladder

organs

The PNS __________ ____________ consist of motor neurons that carry out the motor functions of the NS

motor division

motor output

travels from the brain and/or spinal cord via cranial and spinal nerves of the PNS to muscle cells or __________ for secretion

glands

organs that carry out the effects of the NS

effectors

the motor division may be further classified based on the organs that the neurons contact

2 divisions: ___________ motor division, ____________ motor division

somatic, visceral

somatic motor division

- also called the voluntary motor division

- consists of neurons that transmit signals to __________ _____________

- skeletal muscle tissue is under conscious control

skeletal muscles

visceral motor division

- also called the ANS/involuntary motor division

- consists of neurons that carry signals primarily to where?

- the ANS regulates secretion from certain glands, the contraction of smooth muscle, and the contraction of cardiac muscle in the heart

thoracic and abdominal viscera

what are the 2 primary types of cells in nervous tissue?

neurons, neuroglial cells

Neurons are generally __________ = at a certain point in development, they lose their centrioles and after that lack the ability to undergo mitosis

amitotic

what are the 3 main parts of a neuron?

dendrites, cell body (soma), axon

organelle composition → level of biosynthetic activity

- Free ribosomes and rough ER are found in abundance, reflecting the commitment of the cell body to protein synthesis

- Other organelles involved in protein synthesis (Golgi apparatus and one or more prominent nucleoli) are present

- __________________ are numerous, indicating the high metabolic demands of the neuron

- The cytoplasm of the cell includes lysosomes, smooth ER, and other organelles found in most cells

Mitochondria

dendrites

- Short, highly forked processes that resemble the branches of a tree limb

- Receive input from other neurons, which they transmit in the form of electrical impulses toward the cell body

- Do not generate or conduct ___________ ________________

Huge receptive surface area

action potentials

_________ = nerve fiber = processes that can generate and conduct APs

1 axon per neuron

axon

the initial portion of an axon where an AP is generated

axon hillock

branches that extend from some axons that typically arise at right angles

axon collaterals

small branches at the end of an axon that are a result of the splitting of both the axon and its collaterals

telodendria

location of termination of telodendria; also called synaptic knobs; role is to communicate with a target cell; each axon generally splits into >1000

axon terminals

the plasma membrane of the axon

axolemma

cytoplasm of the axon

axoplasm

what are the 3 functional regions of the neuron?

receptive region, conducting region, secretory region

receptive region of neuron

consists of what 2 structures?

dendrites and cell body.

conducting region of neuron

The received signals are collected in the cell body, which then may transmit a signal to the ________, the conducting region of the neuron.

axon

secretory region of neuron

When the signal reaches the axon terminals of the secretory region, they secrete chemicals that trigger changes in their __________ cells.

target

what are the 3 structural classifications of neurons?

multipolar, bipolar, pseudounipolar

multipolar neuron

- A neuron with 1 axon and >2 ____________

- Over 99% of neurons in the body

- Widest variety in terms of shape and size

- motor (efferent) neurons, interneurons

dendrites

bipolar neurons

- how many axons and dendrites do bipolar neurons have?

- cell body in middle

- In humans, the majority of bipolar neurons are sensory neurons, located in places such as the retina of the eye and the olfactory epithelium of the nasal cavity

1 axon, 1 dendrite

pseudounipolar neurons

how many axons does pseudounipolar neurons have?

2

pseudounipolar neurons

- 2 axons: a _____________ process that brings input to the cell body and a ____________ process that brings input to a target cell; formerly referred to as unipolar neurons

- sensory neurons that detect stimuli such as touch, pressure, and pain

peripheral, central

what are the 3 functional classifications of neurons?

sensory (afferent), interneuron, motor (efferent)

cluster of neuron cell bodies in the CNS

nuclei

cluster of neuronal cell bodies in the PNS

ganglia

bundles of axons in the CNS

tracts

bundles of axons in the PNS

nerves

____________ = type of neuroglial cells in the CNS that anchor neurons and blood vessels, regulate extracellular environment, facilitate formation of BBB, repair damaged tissue

astrocytes

____________ = type of neuroglial cells in the CNS that myelinate certain axons in the CNS

oligodendrocytes

____________ = type of neuroglial cells in the CNS that act as phagocytes

microglia

____________ = type of neuroglial cells in the CNS that line cavities, cilia circulate fluid around brain and spinal cord, some secrete CSF

ependymal cells

____________ = type of neuroglial cells in the PNS that myelinate certain axons

Schwann cells

____________ = type of neuroglial cells in the PNS that surround and support cell bodies

satellite cells

____________ is composed of repeating layers of the plasma membrane of the neuroglial cell, so it has the same substance as any plasma membrane: phospholipids, other lipids like cholesterol, and proteins

Myelin

myelin sheath

- plays an important role in the electrophysiology of many neurons

- in unmyelinated axons, the electric current "leaks" out of the axon and has to be continually regenerated

- however, ions do not pass easily through the hydrophobic portion of the phospholipid bilayer → the high lipid content of myelin makes it an excellent insulator, akin to the rubber tubing around a copper wire

- overall effect of this insulation is to increase the speed of _______________ of action potentials: Myelinated axons conduct action potentials about 15-150 times faster than unmyelinated axons.

conduction

the myelinated segment of an axon; covered by neuroglia

internodes

are more than 1 cell needed to myelinate an axon in the CNS and PNS?

yes (axons are generally much longer than a single oligodendrocyte or Schwann cell)

the unmyelinated segment of an axon between two internodes

node of Ranvier (myelin sheath gap)

collections of myelinated axons that appear white

white matter

collections of unmyelinated axons, dendrites, and cell bodies that appear gray

gray matter

Can damaged neurons in the CNS regenerate?

no (damaged axons and dendrites in the CNS almost never regenerate)

Neural tissue in the PNS is capable of regeneration to some extent, but only if the ______ _________ remains intact

cell body

which of the 3 functions of the NS (sensory, integrative, motor) are carried out by the PNS?

sensory, motor

internal cavities of the brain that are filled with a protective cerebrospinal fluid

ventricles

the brain is (richly/poorly) supplied with blood vessels

richly

what are the 4 divisions of the brain?

cerebrum, diencephalon, cerebellum, brainstem

4 divisions of brain

______________

- higher mental functions

- interprets sensory stimuli

- plans and initiates movement

cerebrum

4 divisions of brain

_______________

- processes, integrates, and relays information

- maintains homeostasis

- regulates biological rhythms

diencephalon

4 divisions of brain

____________________ monitors and coordinates movement

cerebellum

4 divisions of brain

______________

- maintains homeostasis

- controls certain reflexes

- monitors movement

- integrates and relays information

brainstem

where does the spinal cord begin?

foramen magnum (of the occipital bone)

the spinal cord is encased within and protected by what?

vertebral cavity

Like the brain, the spinal cord has an internal cavity filled with cerebrospinal fluid; its cavity, the ___________ ___________, is continuous with the ventricles of the brain.

central canal

in the brain, the gray matter is on the (outside/inside) and the white matter is on the (outside/inside)

outside, inside

in the spinal cord, the gray matter is on the (outside/inside) and the white matter is on the (outside/inside)

inside, outside

white matter in the spinal cord is called what?

tracts

gray matter in the spinal cord is called what?

nuclei

name 4 things that help protect the brain

cranial cavity (skull), cranial meninges, CSF, BBB

the cranial meninges, CSF, and BBB are (inside/outside) the skull

inside

what is the singular form of meninges?

meninx

List the three cranial meninges from outermost to innermost.

dura mater, arachnoid mater, pia mater (DAP)

What are the three spaces related to the meninges?

epidural space, subdural space, subarachnoid space

Spaces of the meninges

potential space between the dura mater and the cranial bones

epidural space

Spaces of the meninges

narrow space deep to the dura that houses a thin layer of serous fluid and certain veins that drain the brain

subdural space

Spaces of the meninges

narrow, fluid-filled space between the arachnoid mater and pia mater that contains CSF and major blood vessels of the brain

subarachnoid space

What are the two layers of the dura mater?

periosteal dura, meningeal dura

layers of the dura

____________ dura = outer layer that is attached to the inner surface of the cranial cavity, functions as the periosteum of the bones and has an extensive blood supply that resides in the epidural space

periosteal

layers of the dura

____________ dura = inner layer that is avascular; lies superficial to the arachnoid mater

meningeal dura

the set of venous channels that are located between two layers of dura mater (periosteal layer, meningeal layer) and drain the cerebral veins of the brain

dural sinuses

a double fold of meningeal dura that dives into the longitudinal fissure and separates the 2 cerebral hemispheres

falx cerebri

the ________ ______________ separates the left and right cerebellar hemispheres

falx cerebelli

this is the the partition between the cerebellum and the occipital lobe of the cerebrum; named for its resemblance to a tent covering the cerebellum

tentorium cerebelli

the arachnoid mater resembles a what?

spider web

inward extensions made of bundles of collagen fibers and fibroblasts that anchor the arachnoid mater to the deeper pia mater

arachnoid trabeculae

arachnoid granulations = arachnoid _________: play an important role in returning CSF to the bloodstream

villi