A&P - Lecture 3

What is the overall job of the nervous system?

To detect changes inside and outside the body and respond to them, controlling and integrating bodily activity

What is the difference between the afferent and efferent information?

Afferent = sensory, travels toward the CNS

Efferent = motor, travels away from the CNS to an effector

Sensory information is carried by which type of neuron, and in which direction does it travel

Afferent neurons, up toward the brain (ascending)

Motor information is carried by which type of neuron, and in which direction does it travel?

Efferent neurons (away from the brain, exiting the spinal cord)

What structures make up the CNS? What makes up the PNS?

CNS = brain + spinal cord

PNS = everything else (cranial nerves, spinal nerves, ganglia, enteric plexuses, sensory receptors)

What is the difference between the somatic and autonomic nervous systems?

Somatic = information you control (skeletal, muscle, voluntary)

Autonomic = things you don’t consciously think about (e.g. heartbeat)

Why do the sympathetic and parasympathetic systems each do?

Sympathetic = “fight, flight, fright”

Parasympathetic = “rest, relaxation, rumination” (SLUDD)

Why is the nervous system described as bidirectional?

Information flows in both directions: sensory up to the brain, motor, down to the body

Which part of the nucleus contains the nucleus and most organelles?

Cell body (perikaryon/soma)

Which part of the neuron receives incoming signals from other neurons?

Dendrites

Where do action potentials start on a neuron, and what triggers them?

At the trigger zone (axon hillock), when summed graded potentials reach threshold

What is a node of Ranvier?

A gap in the myelin sheath where the axon membrane is exposed

Where on a neuron are ligand-gated Na+ channels found, and what do they produce?

Dendrites and cell body; graded potentials

Where on a neuron are voltage-gated Na+ channels found, and what do they produce?

Trigger zone and axon; action potentials

Where on a neuron are voltage-gated Ca2+ channels found, and what do they do?

Axon terminal; Ca2+ entry triggers neurotransmitter release

Which neuron shape is efferent and where is it found?

Multipolar (ANS motor, skeletal muscle control, interneurons)

Which neuron shape is afferent, and where is it found

Pseudounipolar (sensory signaling), with a central process and a peripheral process

What is an interneuron?

A neuron located entirely in the CNS that connects sensory and motor neurons

What fraction of all neurons are interneurons?

About 99%

How do neuroglia differ from neurons?

They are nonneuronal and nonexcitable (they don’t transmit signals), but they support, insulate, and nourish neurons; about 5x more abundant than neurons

Name the four neuroglia of the CNS

Oligodendrocytes, astrocytes, ependymal cells, microgliaN

Name the two neuroglia of the PNS

Schwann cells and satellite cellsWhich

Which glial cell make myelin?

Oligodendrocytes (CNS) and Schwann cells (PNS)

What two factors make an axon conduct faster

Larger diameter and myelination

Why do thick axons conduct faster?

They offer less resistance to ion flow

What do myelin do?

It insulates the axons so that one the gaps (nodes of Ranvier) must depolarize

What is saltatory conduction?

Action potentials jump from one node of ranvier to the next along a myelinated axon, which is much faster than continuous conduction

How does conduction work in an unmyelinated axon?

Slow depolarization of every section of membrane in turn

One oligodendrocyte vs One Schwann Cell: How does each myelinate?

Oligodendrocyte: Several sheaths, sections of several axons

Schwann cell: one sheath, one section of one axon

Which myelinating cell regenerates after damage?

Schwann cells (PNS); oligodendrocytes (CNS) do notW

Multiple sclerosis affects which part of the nervous system, and which cell is involved?

CNS: oligodendrocytes

Does multiple sclerosis impair conduction or transmission, and why?

Conduction, because the myelinated axons (which carry the electrical signal) are damaged

Why is MS so hard to recover from?

Oligodendrocytes won’t repair themselves, and one oligodendrocyte myelinates many axons, so loss causes widespread secondary demyelination

What is the course and prognosis of MS?

Slow progression; life expectancy drops 7-14 years; no cure, but remission can occur

Guillain-Barré syndrome affects which part of the nervous system?

PNS

What is the course and prognosis of Guillain-Barré?

Progresses over days to weeks; 80–90% recover within 2–4 weeks

Why do people recover from Guillain-Barré but not MS?

Schwann cells can dedifferentiate, proliferate, and remyelinate bare axons; oligodendrocytes can’t

What does the cerebral cortex do?

Thinking, memory, voluntary motor movement, and sensory perception

What does the diencephalon do?

Relays sensory and motor information; autonomic functions

What does the brainstem do?

Autonomic functions and cranial nerves

What does the cerebellum do?

Coordination of movement and balance

What does the spinal cord do?

Motor output, sensory input, reflexes, and interface with the PNS

What is grey matter made of, and what is its function?

Nerve cell bodies; connections and transmission (processing)

What is white matter made of, and what is its function?

Myelinated axons, conduction

What are grey matter and white matter called in the CNS vs. the PNS?

Grey Matter: Cortex/Nuclei (CNS), Ganglia (PNS)

White Matter: Tracts/Pathways (CNS), Nerves (PNS)

What do proximal and distal mean?

Proximal = closer to the point of attachment (trunk)

Distal = farther from it

What do medial and lateral mean?

Medial = toward the midline

Lateral = away from the midline

What do superior and inferior mean?

Superior = Toward the head

Inferior = Toward the feet

What do anterior and posterior mean?

Anterior = Front

Posterior = Back

In neuroanatomy, What do dorsal and ventral mean?

Dorsal = toward the top of the brain/back of the spinal cord

Ventral = toward the bottom of the brain/front of the spinal cord

In neuroanatomy, what do rostral and caudal mean?

Rostral = toward the front of the brain/top of the spinal cord

Caudal = Toward the back of the brain/bottom of the spinal cord

Why are the rostral/caudal.dorsal/ventral simpler in a dog than a human?

A dog’s head is in line with its spine, but in humans the brain bends relative to the spinal cord

What is an eponym? Give two examples

A term named after a person or myth (e.g. fallopian tube, Achilles’ heel)

What is the pyramidal tract also called?

The corticospinal tract

Which plan divides the brain into front and back parts?

Coronal

Which plane divides the brain into left and right parts?

Sagittal

Which plan divide the brain into upper and lower parts

Transverse

What is the difference between a fissure, a sulcus, and a gyrus?

Fissure = deep groove

Sulcus = shallow groove

Gyrus = ridge

What are the three components of the cortex?

1. Superficial grey matter (cell bodies)

2. White matter tracts (axons)

3. Deep nuclei (cell bodies)

What is the function of each cortical component?

Grey matter = specialized areas where processing happens

White matter = connections

Deep nuclei = integrated functions and points where pathways connect

Where are the deep nuclei located

Around the ventricles, lateral to the thalamus

Name the five lobes of the cortex

1. Frontal

2. Parietal

3. Temporal

4. Occipital

5. Insula

What does the central sulcus separate?

The frontal lobe (motor, in front) from the parietal lobe (sensory, behind)

What does the lateral (Sylvian_ fissue separate, and what is hidden inside it?

The temporal lobe from the frontal and parietal lobes; the insular lobe (it can open to show it)

What does the longitudinal fissure separate?

The two cerebral hemispheres

What does the parieto-occipital sulcus separate?

The parietal and occipital lobes (visible on the medial surface)

Is the cerebellum part of the cortex?

No

Which lobe handles behaviour, emotional control, personality, problem-solving, and voluntary movement?

Frontal

Which gyrus controls voluntary movement, and where is it?

Pre-central gyrus, in the frontal lobe just anterior to the central sulcus

If the pars opercularis is damaged, what happens?

Difficulty producing language (expressive aphasia, Broca’s); it’s in the frontal lobe

Which lobe integrates touch, pain, proprioception, and temperature?

Parietal

Which gyrus receives touch information, and where is it?

Post-central gyrus, in the parietal lobe just posterior to the central sulcus

If the posterior superior temporal gyrus is damaged, what happens?

Difficulty understanding speech (receptive aphasia, Wernicke’s)

What are the functions of the temporal lobe?

Auditory processing, language (semantics and naming), and smell

Which lobe processes vision?

OccipitalWh

What is the homunculus?

A somatotopic map on the pre- and post-central gyri, drawn in proportion to the amount of innervation each body part has

Which functions are associated with the left vs right hemisphere?

Left: analytical, logical, scientific, mathematical, language

Right: holistic, intuitive, creative, artistic, musical

What are commissural fibers, and what is an example?

Fibers that connection the two hemispheres (e.g. corpus callosum)Wh

What are the association fibers, and what is an example?

Fibers that connect lobes within the same hemisphere (e.g. Fornix)

What are projection fibers, and what is an example?

Fibers that connect the cortex to other parts of the CNS (e.g. internal capsule: memory and sensory tracts)

What does the limbic system do, and where is it?

Memory and emotion; around the inside of the ventricles

Name the limbic system structures

Amygdala, hippocampus, fornix, mammillary bodies

What do the basal nuclei (basal ganglia) do, and where are they?

Basic motor function; around the outside of the ventricles

Name the basal nuclei

Caudate, putamen, globus pallidus