Lecture 5: Organization of the Nervous System

function of the NS

• receive sensory information

• integrate and interpret information

• generate appropriate motor responses

• maintain homeostasis

stimulus → sensory input → CNS integration → motor output

What is the major functional unit of the nervous system?

neuron

What are the two nervous system cell types?

neurons

glial cells

neuron

functional unit of the nervous system

generate action potentials

dendrites receive information

soma performs metabolic functions

axon conducts action potentials

axon terminal communicates with target cells

glial cells

support neuronal function

• produce myelin

• support neuronal metabolism

• maintain extracellular ion balance

• remove NTs

• participate in immune defense

• support synaptic function

dendrites…

receive information

the soma…

performs metabolic functions

the axon…

conducts action potentials

the axon terminal…

communicates with target cells

Major divisions of the nervous system

CNS

• contains sensory, motor, and integrative functions (processing center)

• brain

• spinal cord

Peripheral nervous system (PNS)

• autonomic nervous system (ANS)

  • sympathetic nervous system

  • parasympathetic nervous system

• Somatic nervous system

  • sensory

  • motor

peripheral nervous system

• composed of spinal and cranial nerves

• has both afferent (sensory) and efferent (motor) axons

• peripheral nerve axons converge to form a single spinal nerve at each intervertebral foramina

  • afferent sensory axons enter spinal cord via dorsal roots

  • efferent motor axons exit spinal cord via ventral roots

afferent axons

• sensory

• towards CNS

• carry action potentials from peripheral sensory receptors to the CNS

• axons enter spinal cord via dorsal roots

efferent axons

• motor

• away from CNS

• carry action potentials away from CNS to synapses

• axons exit spinal cord via ventral roots

Somatic sensory signals come from _________, and motor signals go to ________.

skin and muscles

skeletal muscle

Visceral sensory signals. come from ________ and motor signals go to __________.

thoracic and abdominal organs

smooth m., cardiac m., and glands

5 major brain regions

brainstem

• medulla

• pons

• midbrain

forebrain

• diencephalon

• telencephalon

What are the 3 regions of the brain that make up the brainstem, and what is their main function?

medulla, pons, midbrain

receive sensory input from and supplies motor output to the face and head

What are the 2 regions of the brain that make up the forebrain, and what is their main function?

diencephalon and telencephalon

• most sophisticated info processing

• motor output

What CNS region relays sensory information to the brainstem (can bypass brainstem if needed)?

spinal cord

brainstem

relays sensory information to the forebrain

relays motor commands between forebrain and spinal cord

forebrain (cerebrum)

sophisticated information processing

can bypass brainstem and send motor commands directly to spinal cord

What CNS region has sensory dorsal root axons that carry action potentials originating in skin, muscles, tendons, joints, visceral organs to spinal cord?

spinal cord

What CNS region contains cell bodies and dendrites of motor neurons whose axons exit ventral roots to travel to smooth or skeletal muscle?

spinal cord

Which CNS region contains tracts of axons carrying sensory info to brain and motor commands from the brain to motor neurons?

spinal cord

What CNS region can control muscle stretch reflexes and limb withdrawl from painful stimuli?

spinal cord

Which CNS region has functions in cardiovascular regulation, respiratory regulation, swallowing, digestion, and vocalization?

medulla

Which CNS region has functions in facial sensation, mastication, and relay to cerebellum?

pons

Cranial nerve nuclei are clusters of ___________.

neuronal cell bodies

Which CNS region contains superior and inferior colliculi for visual and auditory reflexes?

midbrain

The superior colliculus is located in which region of the CNS, and mediates what reflexes?

midbrain

visual

The inferior colliculus is located in which region of the CNS, and mediates what reflexes?

midbrain

auditory

Which CNS region contains cranial nerve nuclei to control eye movement and induce pupillary constriction?

midbrain

What is the reticular formation? What CNS region(s) contain it?

a netlike complex of small clusters of cell bodies and axonal projections located near the midline

modulates consciousness, pain perception, spinal reflexes, and movement

each brainstem region contains a portion of it (medulla, pons, midbrain)

What area of the brain modulates consciousness, pain perception, spinal reflexes, and movement?

reticular formation

Which CNS region contains the thalamus and hypothalamus?

diencephalon

Which area of the brain acts as a relay station for and a modulator of info being passed to the cerebral cortex from sensory systems and other brain regions?

thalamus

Which area of the brain regulates the ANS, controls hormone secretion from the pituitary, and maintains homeostasis by regulating autonomic and endocrine function?

hypothalamus

True or False: The hypothalamus has several subnuclei, while the thalamus does not.

False: both the thalamus and hypothalamus have several subnuclei

parts of the telencephalon

cerebral cortex

basal ganglia

hippocampus

Which region of the brain contains the cerebral cortex, basal ganglia, and hippocampus?

telencephalon

Which area of the brain uses complex sensory integration (such as somatic senses, vision, olfactory, taste, hearing, etc.), concious sensory perception, and executes sequences of voluntary movement?

cerebral cortex

Which area of the brian modulates motor functions of the cerebral cortex?

basal ganglia

Which area of the brain is responsible for memory and spatial learning?

hippocampus

The CNS is protected and surrounded by 3 protective layers called ________.

meninges (dura mater, arachnoid, pia mater)

From external to internal, name the 3 meninges.

dura mater

arachnoid

pia mater

Which meninge consists of a thicker layer of fibroblast cells, and is fused with the inner bine surface fo the skull?

dura mater (outermost layer)

Which meninge consists of a thin layer of fibroblast cells and has a spiderweb-like appearance?

arachnoid (middle layer)

The subarachnoid space traps ______ in between the ______ and ______ meninges.

CSF

arachnoid

pia mater

Which meninge consists of a single layer of fibroblast cells?

pia mater (innermost layer)

What is the order of the brain layers from external → internal?

Bone → dura mater → subarachnoid space → CSF → pia mater → brain

The cerebrospinal fluid (CSF) is ultrafiltrate of _____. What color is it, and how is it produced?

plasma

clear and colorless

by choroid plexus in each of the 4 ventricles

Modified _____ cells joined by tight junctions surrounding a core of fenestrated capillaries form a ______-________ barrier.

ependymal

blood-CSF

Describe the flow of the CSF.

CSF circulates through ventricles → flows into subarachnoid space → returns to venous circulation

What are the mechanical functions of the CSF?

cushion CNS

equalize pressure

What are the chemical functions of the CSF?

stable extracellular environment

buffer pH (constantly detected by respiratory center near surface of medulla)

What are the transport functions of the CSF?

nutrient exchange

waste removal

The tight junctions of the blood brain barrier (BBB) prevent many molecules from leaving the blood and entering the brain. what forms and maintains these junctions? How do they do this?

astrocytes

• interacts with brain endothelial cells

• regulates permeability by secreting substances

What characteristics must a molecule have to cross the BBB?

• small, uncharged

• lipid-soluble

  • glucose and amino acids can pass, but require transport

• non-protein bound

• O2 and CO2

Some substances allowed through the BBB may be pumped back into the bloodstream by the ______ pump.

MDR

What are some examples of substances that do NOT readily cross the BBB?

• many proteins

• many antibiotics

• large, polar molecules