A&P 1 Ch. 11/12 Objectives - McClelland

Describe the major functions of the nervous system

- sensory: detects internal & external stimuli

- integrative: processes & interprets sensory stimuli to determine an appropriate response

- motor: produces a response (muscle movement or gland secretion)

- general control: directs voluntary movement & is the seat of consciousness, personality, learning, & memory

Describe the structures and basic functions of each organ of the central and peripheral nervous systems

- CNS: comprised of the brain & spinal cord

- PNS: comprised of nerves that carry signals to & from the CNS

--> this includes 12 pairs of cranial nerves & 31 pairs of spinal nerves

Explain the major differences between the two functional divisions of the peripheral nervous system

- sensory (afferent): sends info TO CNS

---> somatic (skin, muscles, senses)

---> visceral (organs)

- motor (efferent): sends commands FROM CNS

---> somatic: voluntary (skeletal muscle)

---> autonomic: involuntary (smooth muscle, heart, glands)

Describe the structure and function of each component of the neuron

neurons transmit signals via action potentials --> key parts:

- cell body: metabolic center

- dendrites: receive input & transmit it toward the cell body

- axon: sends action potentials away from cell body (starts at axon hillock & ends at axon terminals)

Structural Classification:

- multipolar: one axon & multiple dendrites

- bipolar: one axon & one dendrite (found in the retina & olfactory epithelium)

- pseudounipolar: a single short process that splits into two axons; detects touch, pressure, & pain

Functional Regions:

- sensory (afferent): carry signals toward the CNS

- interneurons: relay messages within the CNS (majority of neurons)

- motor (efferent): carry signals AWAY from the CNS to muscles & glands

Astrocyte

description:

- star-shaped cells with a central portion & processes that terminate in End-Feet

location:

- CNS

function:

- support neurons, regulate environment, help form blood-brain barrier

Microglia

description:

- tiny, branching cells that are activated by brain injury

location:

- CNS

function:

- become wandering phagocytes (clean up debris, pathogens)

Ependymal

description:

- ciliated cells

location:

- CNS

function:

- produces & circulate CSF

Oligodendrocyte

description:

- ciliated cells

location:

- CNS

function:

- produces & circulate CSF

Schwann cells

description:

- encase axons of neurons in the PNS

location:

- PNS

function:

- wrap around axons & aid repair

Satellite Cells

description:

- flat cells that surround neuron cell bodies

location:

- PNS

function:

- regulate environment around neurons

Describe the voltage-gated ion channels that are essential for the development of the action potential

- sodium

- potassium

Depolarization

voltage-gated Na+ channels open, making the membrane potential more positive

Repolarization

Na+ channels close & voltage-gated K+ channels open, returning the potential toward resting levels

Hyperpolarization

K+ channels remain open briefly, making the membrane more negative than resting potential

Absolute Refractory Period

no additional stimulus can produce an action potential

Relative Refractory Period

only a very strong stimulus can trigger an action potential

Saltatory Conduction

fast conduction in myelinated axons where the signal "jumps" between Nodes of Ranvier

Continuous Conduction

slower conduction in UNmyelinated axons

Explain how axon diameter and myelination affect conduction speed

conduction speed is increased by larger axon diameter & myelination

Electrical Synapse

allow near-instantaneous, bidirectional signal transmission via direct ion flow through gap junctions, perfect for synchronization

Chemical Synapse

the junction where neurons communicate via chemical messengers, comprising of three primary components:

- presynaptic (sending signal)

- synaptic cleft (gap)

- postsynaptic (receiving signal)

Discuss the relationship between a neurotransmitter and its receptor

- "lock and key" mechanism

- crucial for brain communication

- neurotransmitter (key) is a key chemical messenger that binds to a specific receptor (lock) - a protein on the surface of a neuron - to pass a message & trigger electrical or chemical changes

Describe the events of chemical synaptic transmission in chronological order

1. action potential arrives

2. calcium influx

3. vesicle fusion

4. neurotransmitter release

5. binding to receptors

6. subsequent inactivation

Excitatory Postsynaptic Potential (EPSP)

a temporary depolarization of a postsynaptic neuron's membrane potential caused by the inflow of positively charged ions

Inhibitory Postsynaptic Potential (IPSP)

temporary hyperpolarizations of a postsynaptic neuron membrane caused by the flow of negatively charged ions into or positively charged ions out of the cell

Temporal Summation

when neurotransmitters are released repeatedly from the axon terminal of a single presynaptic neuron

Spatial Summation

simultaneous release of neurotransmitters from the axon terminal of multiple presynaptic neurons

Explain how a single neurotransmitter may be excitatory at one synapse and inhibitory at another

- most can have both excitatory & inhibitory effects, depending on the receptor

- each neurotransmitter can also have several receptor types

Describe the structural and functional properties of the major classes of neurotransmitters

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Describe the most common excitatory and inhibitory neurotransmitters in the CNS

- substance P

- opioids

- neuropeptide Y

Define a neuronal pool, and explain its purpose

groups of interneurons within the CNS that perform a common function defined by the synaptic connections of that pool

Diverging Circuits

begins with one axon of an input neuron branching to make contacts with multiple postsynaptic neurons which then branch to more neurons, & so on

- allow a single neuron to communicate with multiple parts of the brain &/or body

Converging Circuits

axons from multiple input neurons converge onto a single postsynaptic neuron, allowing for spatial summation of synapses

Frontal Lobe

- primary motor cortex

- planning

- personality

- language production (Broca's area)

Parietal Lobe

- processes somatosensory information --> touch, temperature, pressure, & pain

- handles spatial awareness

Temporal Lobe

- processes auditory information

- processes language comprehension (Wernicke's area)

- stores memories

Occipital Lobe

- visual processing

- color recognition & movement

Insular Lobe

- processes taste

- visceral sensations

Describe the five developmental regions of the brain, and identify the major areas of the adult brain that arise from each region.

- cerebrum: responsible for higher mental functions (learning, memory, personality)

- diencephalon: central core (thalamus etc.); processes/relays info & maintains homeostasis

- cerebellum: posterior/inferior portion involved in planning & coordinating movement

- brainstem: connects the brain to the spinal cord; controls involuntary processes like breathing

Diencephalon (thalamus, hypothalamus, epithalamus)

relays sensory input & regulates endocrine functions

Cerebellum

coordinates voluntary movements & balance

Brainstem (midbrain, pons, medulla oblongata)

regulates cardiovascular, respiratory, & autonomic functions

Limbic System

- located beneath the cerebrum

- processes emotion, memory, & motivation (hippocampus, amygdala)

Reticular Formation

- runs through the brainstem

- controlls consciousness, sleep cycles, & alertness

Endocrine System

uses hormones released into the bloodstream for slower, broad-acting, long-lasting effects (growth, metabolism, long-term balance)

Nervous System

acts rapidly via electrical impulses for immediate reactions (reflexes, short-term adjustments)

Hypothalamus

- primary regulator of homeostasis

- monitors body temperature, blood pressure, hunger, thirst, & the sleep/wake cycle

Provide specific examples demonstrating how the brain responds to maintain homeostasis of regulated physiological variables in the body.

Describe the areas of the cortex responsible for cognition and language.

prefrontal cortex

Discuss the concept of cerebral hemispheric specialization.

- left hemisphere: language production & comprehension, analytical reasoning, logic, & sequential, local visual processing

- right hemisphere: dominates in non-verbal semantic processing, emotional prosody (tone), spatial awareness, facial recognition, & holistic, global visual processing

Describe the parts of the brain involved in storage of long-term memory, and discuss possible mechanisms of memory consolidation.

- hippocampus: encoding & initial consolidation

- neocortex: long-term storage

Cerebrospinal Fluid (CSF)

- provides buoyancy & protection

- produced in ventricles & reabsorbed into the blood

Describe the structural basis for and the importance of the blood brain barrier.

protects brain fluid from blood substances

Identify and describe the CRANIAL meninges, and explain their functional relationship to the BRAIN.

- dura mater: forms dural reflections that compartmentalize the brain & restrict its movement

- arachnoid mater: granulations protrude through the dura into venous sinuses to allow CSF to exit

- pia mater: highly vascularized & supports blood vessels entering the brain tissue

Describe the gross anatomy and location of the spinal cord.

extends from the foramen magnum to L1-L2

Identify and describe the anatomical features seen in a cross-sectional view of the spinal cord.

features internal gray matter (nuclei) & superficial white matter (tracts)

Identify and describe the SPINAL meninges and the spaces between and around them.

1. epidural space: between dura mater & periosteum (bone); filled with epidural fat, CT, & provides padding

2. dura mater: extends from foramen magnum to the sacrum, forming a loose sheath around the spinal cord

3. subdural space: "potential" space between dura & arachnoid; under normal conditions it does not exist unless it fills with blood or fluid due to injury or illness

4. arachnoid mater: bridge the space to the pia mater

5. subarachnoid space: between arachnoid & pia; contains CSF which cushions the spinal cord

6. pia mater: forms the denticulate ligaments between nerve roots that help stabilize the spinal cord

Ascending Tracts

carry signals up to the brain

Descending Tracts

transmit commands down to muscles

Describe the roles of the central and peripheral nervous systems in processing sensory stimuli.

- CNS: acts as the control center, integrating & interpreting sensory data

- PNS: acts as the messenger, detecting stimuli & transmitting signals between the body & the CNS

Describe the locations and functions of first-, second-, and third-order neurons in a sensory pathway.

- 1st: in the dorsal root ganglion or cranial nerve ganglia; detects the stimulus in the periphery & transmits the signal to the spinal cord or brainstem

- 2nd: in the spinal cord's dorsal horn or in the brainstem; relays the signal from the spinal cord/brainstem, usually crossing to the opposite side, & ascends to the thalamus

- 3rd: located in the thalamus for body sensation or ventral posteromedial nucleus; transmits the signal from the thalamus to the primary somatosensory cortex in the parietal lobe of the cerebrum

Explain the ways in which special sensory stimuli are processed by the CNS.

through specialized receptors that transduce stimuli into electrical signals, which are then transmitted via labeled lines to the thalamus (except for olfaction) & finally to dedicated organized cortical areas for perception

Describe the locations and functions of the upper and lower motor neurons in a motor pathway.

- upper: originate in the motor cortex & descend through the brainstem/spinal cord; maintain muscle tone & initiating movement

- lower: start in the brainstem/spinal cord, acting as the final link to directly innervate skeletal muscle fibers

Explain the roles of the cerebral cortex, basal nuclei, and cerebellum in movement.

Describe the overall pathway from the decision to move to the execution and monitoring of a motor program.

Explain how decussation occurs in sensory and motor pathways, and predict how brain and spinal cord injuries affect these pathways.