Unit 1 A&P Exam

CNS

Organs: brain and spinal cord

Function: responsible for integrating and processing information

PNS

includes: cranial nerves and spinal nerves

Function: communication between CNS and rest of the body

Sensory (afferent) division

Somatic and visceral sensory nerve fibers

Conducts impulses from receptors to the CNS

Motor (efferent) division

Motor nerve fibers

Conducts impulses from the CNS to effectors (muscles and glands)
Two divisions (SNS and ANS)

Somatic Nervous System

Controls voluntary motor nerve fibers

Conducts impulses from the CNS to skeletal muscles

Autonomic Nervous System

Regulates involuntary motor nerve fibers

Conducts impulses from the CNS to cardiac/smooth muscle and glands

Two further divisions (Sympathetic and Parasympathetic)

Sympathetic Division

“fight-or-flight” response, increases alertness and metabolic activity, mobilizes body systems during activity

releases adrenaline

Parasympathetic Division

“Rest-and-digest” response, consereves energy & promotes house-keeping functions furing rest/sleep

Gray Matter

Contains neuron cell bodies, dendrites, and nonmyelinated fibers

Found in outer cortex of the brain, deep nuclei, and the central region of the spinal cord

Primarily responsible for processsing and integration of information

White Matter

Composed of myelinated axons that transmit signals between different parts of the CNS

Found in deep regions of the brain and spinal cord

Facilitates communication between gray matter regions

Multipolar Neuron Parts (in order of polarity)

Dendrites: recieve signals from other neurons

Cell Body (Soma): contains the nucleus and organelles; processes incoming signals and is responsible for all biosynthetic activity

Axon Hillock: Initiates/generates action potentials

Axon: transmits electrical signals away from the cell body

Myelin Sheath: increases signal conduction speed

Nodes of Ranvier: gaps in myelin that enable saltatory conduction

Axon Terminals: release neurotransmitters to communicate with other neurons or effectors

CNS Glial Cells - LIST THEM

astrocytes, microglia, ependymal, oligodendrocytes

Astrocytes

Maintain the blood-brain barrier, regulate ions/nutrients, recycle neurotransmitters, and form scar tissue

Oligodendrocytes

Myelinate CNS axons and provide structural support

Microglia

Remove debris, waste, and pathogens via phagocytosis

Act as immune cells

Ependymal Cells

Line brain ventricles and spinal canal, producing, circulating, and monitoring cerebrospinal fluid (CSF)

PNS Glial Cells - LIST

Schwann Cells and Satellite Cells

Schwann Cells

Myelinate axons in the PNS and aid in repair after injury

Satellite Cells

Surround neuron cell bodies in ganglia for support and protection, regulating their environment

Sensation

Detects stimuli from the environment or internal body conditions via sensory receptors

EX: general senses (like touch, pain, temperature, and proprioception) and special senses (like vision, hearing, taste, and smell). 

Integration

Processes and interprets sensory information to determine appropriate responses

Occurs within CNS in Phe brain and spinal cord

Response

Produces motor output to muscles or glands, either voluntarily (somatic) or involuntary (autonomic)

Ganglia

Found in the PNS

Nuclei

found in the grey matter of the CNS

Tract

a bundle of axons, or fibers, found in the CNS

Nerve

a bundle of axons, or fibers found in the PNS

Myelin Sheath

A white lipoprotein that insulates and protects axons, increasing nerve impulse speed

How is myelin formed in the PNS?

Schwann cells wrap around a single axon, squeezing out cytoplasm to form a tightly layered sheath

How is myelin formed in the CNS?

Oligodendrocytes extend processes to myelinate multiple axons (up to 60 at once)

What is resting membrane potential?

-70mV

Sodium-Potassium Pump (Na/K +ATPase)

Pumps 3 Na+ out, 2 K+ in, using ATP

Leak Channels

K+ leaks out more than Na+ enters, making the inside more negative

Negatively Charged Proteins

Large anions inside the cell further contribute to negativity

Parts of an Action Potential

1. Resting State

2. Depolarization

3. Rising phase of AP

4. Falling phase of AP

5. Undershoot

Depolarization

Voltage-gated Na+ channels open, allowing Na+ influx, making the inside more positive

Peak of AP

(~+30mV): Na+ channels close, and K+ channels open

Repolarization of AP

K+ exits, restoring negativity

Hyperpolarization

Excessive K+ efflux causes a brief dip below resting potential

Absolute Refractory

The time from the opening of Na⁺ channels until they reset - AP cannot occur

Refractory Period

The time in which a neuron cannot trigger another action potential (AP)

Relative Refractory

The period following the absolute refractory period when another AP can only be triggered by an exceptionally strong stimulus

EPSP

Depolarization of the postsynaptic membrane - brings neuron closer to threshold

• caused by Na+ or Ca²⁺ influx

IPSP

hyperpolarization of the neuron - moves it away from threshhold

• Caused by: K+ efflux or Cl⁻ influx

Cause of EPSP and IPSP

The synapse—a structure that allows a neuron to pass an electrical or chemical signal to another cell

Presynaptic neuron

neuron conducting impulses toward synapse (sends info).

Postsynaptic Neuron

neuron transmitting electrical signal away from synapse (recieves info)

• In the PNS, the postsynaptic cell can be a neuron, muscle cell, or gland cell

Chemical Synapse

Chemical signal - neurotransmitter is released from presynaptic neuron

Electrical Synapse

uses gap junctions to send signals from pre to post synaptic neuron

Synaptic Delay

The time required for neurotransmitter release, diffusion, and receptor binding (0.3–5.0 ms). It is the rate-limiting step of neural transmission

Effect of Synaptic Delay

• Action potential transmission down an axon is fast, but the synapse slows transmission to the postsynaptic neuron

• This delay is not noticeable because it is still very quick

Neurotransmitters

Effects can be excitatory (depolarizing) and/or inhibitory (hyper polarizing)

Acetylcholine

excitatory to vertebeate skeletal muscles; excitatory or inhibitory everywhere elese

Secretion sites: CNS, PNS; vertebrate neuromuscular junction

Norepineohrine

Excitatory or inhibitory - biogenic amines

Secretion sites: CNS; PNS

Dopamine

Generally excitatory; may be inhibitory at some sites - biogenic amines

Sites: CNS;PNS

Serotonin

Generally inhibitory - biogenic amines

Sites: CNS

GABA

inhibitory Amino Acid

Site: CNS; invertebrate

Glycine

Inhibitory Amino Acid

Site: CNS

Glutamate

Excitatory Amino Acid

Site: CNS; invertebrate neuromuscular junction

Aspartate

Excitatory Amino Acid

Site: CNS

Substance P

Excitatory - neuropeptide

Site: CNS; PNS

Met-enkephalin

Inhibitory - Neuropeptide

Site: CNS

Where does the embryonic nervous system develop?

The nervous system originates from the ectoderm, specifically the neuroectoderm

Neural plate

develops from part of the ectoderm and then turns into neural groove

Neural groove

develops from neural plate - these neural folds come together to form the neural tube and crest

What does the neural crest become?

PNS

What does the neural tube become?

CNS

Embryonic Structures —> Adult

Forebrain —> Telencephalon & Diencephalon
Midbrain —> Mesencephalon
Hindbrain —> Metencephalon & Myelencephalon

Telencephalon

Cerebrum (includes cerebral cortex, white matter, basal nuclei)

Diencephalon

Diencephalon (thalamus, hypothalamus, epithalamus)

Mesencephalon

Midbrain (part of brainstem)

Metencephalon

Pons (part of brainstem), cerebellum

Myelencephalon

Medulla oblongata (part of brainstem)

Major Regions of the Adult NS

• Cerebrum (including cerebral cortex, white matter, basal nuclei)

• Diencephalon (thalamus, hypothalamus, epithalamus)

• Brainstem (midbrain, pons, medulla oblongata)

• Cerebellum

• Spinal cord

Frontal Lobe

• Located at the front of the brain (behind the forehead)

• Controls movement, thinking, planning, and decision-making

• Broca’s area (left side) helps with speech

Parietal Lobe

• Located behind the frontal lobe, at the top of the brain

• Processes touch, pain, and temperature

• Helps with spatial awareness and movement coordination

Temporal Lobe

• Located on the sides of the brain (near the ears)

• Processes sounds (hearing)

• Helps with memory and learning

• Wernicke’s area (left side) helps understand language

Occipital Lobe

• Located at the back of the brain

• Processes vision (color, shape, motion)

Central Sulcus

• Deep groove separating the frontal and parietal lobes

• Divides motor control (front) and sensory processing (back)

Lateral Sulcus

• Separates the frontal and parietal lobes from the temporal lobe

• Divides auditory areas from motor and sensory regions

Corpus Callosum

• Thick nerve band deep in the brain

• Connects the left and right hemispheres for communication

Commissural fibers

WHITE MATTER
horizontal fibers that connect gray matter of two hemispheres

Association fibers

WHITE MATTER

horizontal running fibers that connect different parts of same hemisphere

Projection fibers

WHITE MATTER

vertical fibers that connect hemispheres with lower brain or spinal cord

Internal capsule

projection fibers on each side of brain stem form compact band
- Passes between thalamus and some of basal nuclei

Corona radiata

WHITE MATTER

projection fibers that radiate through cerebral white matter to cortex

basal ganglia function

movement, decision making and reward/addiction

Diencephalon Location

Between brainstem and cerebrum

Diencephalon Function

memory processing and emotional response, relay and control center

Midbrain

BRAIN STEM

coordinates sensory representations of the visual, auditory, and somatosensory perceptual spaces

Pons

BRAIN STEM

main connection with the cerebellum

Medulla Oblongata

• signals nerves to and from your body

• Controls heart rate, blood pressure, respiration

• Reflex centers for vomiting, swallowing, coughing

BRAIN STEM

Cerebellum Structure

FILL IN

Brain Stem

connects the cerebrum of the brain to the spinal cord and cerebellum

Limbic System Location

Encircles the upper brainstem, includes parts of the cerebrum (hippocampus, amygdaloid body, cingulate gyrus) and connects to the hypothalamus

Limbic System Function

Emotional responses to odors and memory

Amygdaloid body

• Recognizes angry or fearful expressions

• Assesses danger and triggers fear response

Cingulate Gyrus

• Helps express emotions through gestures

• Aids in resolving mental conflict

Where is the limbic system output?

Hypothalamus

What does the hypothalamus play a role in?

Influences psychosomatic illnesses (stress-related disorders)

What helps form and store memories?

Hippocampus & amygdaloid body

• Storage site of neural stem cells