Anatomy and Physiology Notes

Exam 5 Review

• Average was 75%, lower than the previous exam average.
• Extra credit could bump scores up to 4.1 percentage points; remember to submit extra credit Cahoots on time.
• Exam 6 will cover nervous tissue and systems (spinal cord, brain, major peripheral nerves), not cumulative.
• Exam 6 schedule:
  • Open from Thursday at 1 PM to Monday at 7 PM to provide flexibility.
  • This accommodates students needing to take it over the long weekend.
  • Choice to take it Thursday afternoon or any time through Monday.

Pre-Professional Program Advertisement

• Lake State has a pre-professional program for those interested in medical, PA, pre-pharmacy, or predental programs.
• Articulation agreements with:
  • Michigan State University College of Human Medicine (reserves seats).
  • Central Michigan University Physician's Assistant program (reserves seats).
• Contact the professor for more information.

Diagram Zoom Issue

• A student reported difficulty zooming in on diagrams, especially for the lower arm, making it hard to see what was being pointed to.
• The professor will review the diagrams to see if adjustments can be made.

Flexor Carpi Radialis Question

• The question asked which muscle of the anterior forearm is the flexor carpi radialis.
  • The correct answer is B.
  • The flexor carpi radialis is on the side of the thumb.

Elbow Flexion Question

• The question asked which muscle acts as the antagonist during elbow flexion.
  • The correct answer is the triceps brachii.
• If the question asked for the prime mover in elbow flexion, the answer would be the brachialis.

Dorsiflexion Question

• The question concerned dorsiflexion or heel strike.
• Dorsiflexion is carried out by the anterior muscles of the leg.

Week 6 Labs

• Intro to nervous tissue.
• Basic anatomy of the spinal cord, brain, and peripheral nerves.
• Assignments:
  • Spinal cord model anatomy practice.
  • Lab exercises from the manual (Exercise 16).
  • Brain dissection, brain anatomy review.
  • Lab manual exercise number 17 (brain review questions).
• Preview all of Chapter 12 (nervous tissue, nervous system overview, anatomy of the spinal cord).
• Preview the autonomic nervous system and the anatomy of the brain for Thursday.

Exam 6 Overview

• Exam will cover: nervous tissue, spinal cord and brain anatomy, and a preview of the autonomic nervous system.
• Readings from Chapters 12 and 13.

Basic Types of Neurons

• Three types:
  • Sensory (afferent): Delivers information/signals to the central nervous system (brain, spinal cord).
  • Interneurons: Located within the brain and spinal cord tissue.
  • Motor (efferent): Transmits signals away from the central nervous system.
• Typical relay: sensory neuron -> interneuron -> motor neuron.
• A (afferent) comes before E (efferent) alphabetically.
• All three types are:
  • Excitable: Respond to stimuli.
  • Conductive: Transmit signals.
  • Secretory: Secrete neurotransmitters (NT) to propagate signals.

Glial Cells

• Neurons rely on glial cells to carry out critical functions.
• In the central nervous system:
  • Oligodendrocytes: Myelinate neurons, speeding up signal transmission and insulating the axon's electrical signal.
  • Ependymal cells: Produce cerebral spinal fluid, (CSF = filtrate from blood plasma that keeps the brain buoyant and cleanses the nervous tissue).
  • Microglia: Immune system cells that protect from infections.
  • Astrocytes: Abundant, form the framework of the brain and spinal cord structures, including:
    • Blood-brain barrier: Protects the brain from toxins but also a challenge for pharmaceuticals.
    • Feed neurons and promote communication through synapse formation.
• In the peripheral nervous system:
  • Schwann cells: Myelinate axons.
  • Satellite cells: Function unknown.

Neuron Electrical State

• Neurons respond to stimuli via changes in their electrical state.
• Resting membrane potential: Typically -70 millivolts (mV) in the absence of stimuli.
• Maintained by sodium-potassium pumps (Na+/K+ ATPase):
  • Pumps 3 Na+ out and 2 K+ in, resulting in a net loss of +1 charge.
• Stimulus Introduced:
  • The charge of the neuron goes up.
  • If enough stimulus to reach the threshold (-55 mV), the neuron will fire.

Action Potential

• If the cell reaches the threshold it will fire and create a signal by: action potential.
  • Consists of three steps:
    • Depolarization: A sharp increase in internal charge.
    • Repolarization: The charge plummets back down.
    • Hyperpolarization: A brief drop in internal charge below the resting level.
      • Collectively, these create a signal.

Threshold for Firing

• At threshold, Na+ ion channels open, flooding the inside of the cell with +1 charges, resulting in depolarization (fast Na+ influx).
• Channels open more sluggishly,
  • Potassium (K+) channels open, and K+ diffuses out (efflux), causing repolarization.
    • Potassium leakage leads to hyperpolarization.

Action Potential Animation

• Use ANP revealed animations to view.

How the Brain Interprets Signals

• The brain understands where it's receiving the signal from: neural coding.
  • Neural coding is the brain's way of interpreting what the signal means.
• Qualitative:
  *Type of stimuli. Which nerve is carrying out the action potential/fires?
• Quantitative:
  • Neurons with different thresholds.
  • Not type of stimulus, but amount of stimuli. Amount of stimulus?
    Different thresholds: Very low versus high sensitivities.

Local vs Action Potentials

• Local Potential:
  • Occurs at the dendrite of the neuron when it binds to stimuli.
  • Transmitted from the dendrite to the soma (cell body).
  • Graded: Proportional to the amount of stimulus
  • Decremental: Weakens as it is transmitted
  • Reversible: Can reverse direction towards the dendrites.
• Action Potential:
  • Location: Trigger zone (base of the soma where the axon extends).
  • All-or-none: Completes all three steps (depolarization, repolarization, hyperpolarization).
  • Nondecremental: Does not weaken; strength remains constant down the axon.
  • Irreversible: Transmitted in one direction down the axon.

Animation

• ANP revealed giant purple neuron: action potential propagation.

Spinal Cord Cross Section

*Peripheral nerves connect to the spinal cord.

• Spinal nerves paired. One here and one over here.
  *Spinal nerve itself, are what we termed mixed nerves.Carries both sensory input and motor output signals.
  *Both mixed nerves.
  Seperate
• Dorsal Root:
  *Toward the back is dorsal root, contains sensory signals.
  *Also called the afferent route
  *Afferent/sensory goes to the dorsal gray horn.
• Ventral Root: *This ventral root the motor output is coming out .
  • Connects to the dorsal gray horn by: The gray comas here.Gray commissure.
    *Central canal:channel that filled with cerebral spinal fluid in life. connect to the ventricles of our brain.
    *.White matter superficial.Outside.
    *Gray matter deep.
• white matter: myelinated.
  *Gray matter: unmyelinated.

Meninges and Spaces

• Spinal cord cross section shows internal gray matter, dorsal and ventral horns, outer white matter, and spinal nerve pair connections.
• Meninges: Membranes covering the spinal cord (and brain).
  *3 layers
• Dura mater:
  Fat of epidural space. epidural space.Most superficially have epidural space.
  For anesthesia, Epidural is considered
  Arachnoid mater: middle layer. arachnoid arachnoid mater. in between the arachnoid mater and that pia mater.
  Subarachnoid: It subarachnoid because what lies beneath it?below. So that is cerebral spinal fluid.
  Pia Mater:
  That's The deepest of all the Layers and in that regard if you look at the spinal cord of the pia mater. Pia Maters that lies,Right, they're on the is extremely delicate

Nerve Plexuses

• Nerve Plexuses Overview:
  Animation explaining nerve plexsuses
• Several major nerves of the arm, forearm, and hand.
  radial, median, ulnar, musculo, cutaneous, and axillary. So they point out five.
  Males are muscles posterior. For muscles anterior leg foot and our gigundus.
  sciatic nerve that combines it splits the tibial and common fibular branch.