Comprehensive Study Notes for Exam 6

Spirometer Mouthpieces

• A funny anecdote about finding mouthpieces for a spirometer from 1975 right before class.

Bio 122 Transition

• Dr. Garvin will be teaching Bio 122.
• Transition should be easy because he is experienced with the class and labs.

Exam 6 Details

• Exam opens Thursday at 1:00 AM eastern time and closes Monday at 7:00 AM eastern time.
• Labs are due by 7:00 AM on Monday.
• Complete labs before the test to practice.

Questions and Concerns

• A student asked about the start date of the second half of the course.
• Dr. Garvin is likely giving students space to focus on finishing the first half.
• Expect an email from Dr. Garvin with instructions either before or on Monday.
• Dr. Garvin's email: jGarvan@lssu.edu.
• Contact him on Monday if no instructions are received.

Neuron Review

• Afferent (sensory) neurons: Carry input signals.
• Efferent (motor) neurons: Carry output messages.
• Interneurons: Located in the brain or spinal cord (central nervous system).
• All three neuron types have these common properties:
  • Excitability
  • Conductivity
  • Secretion of neurotransmitters

Neuroglial Cells

• Functions of helper cells in nervous tissue (central vs. peripheral).
• Their function and location within the nervous system divisions should be reviewed.

Action Potential

• Review of the action potential.

• The fluctuation in internal charge results from the opening of voltage-gated ion channels. Sodium channels open first, causing sodium to diffuse into the cell, leading to depolarization. Following that potassium channels open. During repolarization cell loses potassium as it diffuses out of the cell.

• Hyperpolarization occurs due to a slight delay in potassium channel closure, resulting in more potassium loss than sodium gain.

Refractory Periods

• Absolute Refractory Period:

  • Overlaps with depolarization and repolarization.
  • No amount of stimulus will generate another action potential.

• Relative Refractory Period:

  • Occurs during hyperpolarization.
  • Only a very strong stimulus can generate another action potential.

• Refractory periods ensure precision and prevent overwhelming the brain with signals.

Action Potential Properties

• All-or-nothing event.
• Nondecrimental: does not weaken as it travels down the axon.
• Irreversible: goes to completion once depolarization begins.

Action Potential Practice Question

• Question from practice worksheet: Which statement is NOT TRUE about action potentials?
  • a. Action potentials follow an all-or-none law (TRUE).
  • b. Action potentials are nondecremental (TRUE).
  • c. Action potentials cannot be triggered again until the hyperpolarized membrane returns to resting potential (FALSE).
  • d. Action potentials cannot be generated unless a cell reaches threshold (TRUE).
• Answer c is false due to the relative refractory period.

Neural Coding

• Qualitative: Which neuron fires.
• Quantitative: How many neurons are firing and their sensitivity/threshold levels.

Spinal Cord Anatomy

• Sensory input enters the dorsal part of the spinal cord.
• Motor output exits the ventral part of the spinal cord.
• White matter is on the periphery, gray matter is deep.

Signal Transmission

• Afferent (Sensory) Route:

  • Stimulus travels from the hand through the dorsal root to the spinal cord.
  • Sensory signals enter the dorsal gray horn.
  • Ascending white matter tract carries the signal to the thalamus (gatekeeper).
  • Signal arrives at the primary sensory cortex (precentral gyrus) in the cerebrum.
  • The signal is transmitted to a sensory-specific association area for interpretation.

• Efferent (Motor) Route:

  • Motor output is transmitted through the primary motor cortex (postcentral gyrus).
  • Descending tracts carry signals down the spinal cord.
  • Signals exit the ventral gray horn, through the ventral root, to the peripheral nervous system.
    Target effector: skeletal muscle (movement), cardiac/smooth muscle, or glands (e.g., salivary glands).

• Reflex Arc:

  • Bypasses the brain.
  • Signal goes from the dorsal gray horn to an interneuron and then back out.
  • Results in a quicker response.

Meninges and Nerve Plexuses

• Order of meninges (superficial to deep): dura mater, arachnoid, pia mater.
• Epidural space is outside the dura mater.
• Subarachnoid space (between arachnoid and pia mater) is filled with cerebrospinal fluid.
• Nerve plexuses from lab manual table 16.1.

Autonomic Nervous System

• Involuntary, unconscious division.
• Two subdivisions: sympathetic and parasympathetic.
  • Sympathetic: fight or flight (high stress).
    • Higher heart rate, blood pressure and respiratory rates.
    • Whole body effects.
    • Longer lasting effects.
  • Parasympathetic: resting and digesting (relaxed).
    • Heart rate, blood pressure and respiratory rates decrease.
    • Targeted, specific effects (e.g., digestion).
    • Shorter term effects.

Brain Anatomy

• Three main parts of the brain:
  • Forebrain
  • Midbrain
  • Hindbrain

Forebrain structures:

• Cerebrum: Majority of the forebrain; higher thoughts, personality, judgment.
• Thalamus: Gatekeeper for sensory and motor input.
• Hypothalamus: Endocrine gland; critical for certain bodily functions.
• Pituitary gland: part of the endocrine system, connected to the hypothalamus.
• Corpus callosum: Connects the left and right cerebral hemispheres.
• Ventricle: Holds and produces cerebrospinal fluid.
• Gyrus: Tissue fold on the cerebrum.
• Sulcus: Groove between folds on the cerebrum's surface.

Midbrain structures:

• Simple cylindrical area.
• Corpora quadrigemina: Four knobs on the back of the midbrain; allows for visual and auditory reflexes.
  • Quad = 4 knobs.

Hindbrain structures:

• Cerebellum: Smaller version of the cerebrum with finer convolutions.
  • Arbor vitae (tree of life): pattern formed by gray and white matter.
  • Gray matter is superficial, white matter is deep (opposite spinal cord).
• Pons: Swollen region, extension of the brainstem.
• Medulla oblongata: Connects to the spinal cord.

Brain Functions

• Medulla Oblongata: Heart rate and blood pressure regulation (a); Gag reflex (g).
• Cerebrum: Speech, personality, social judgment (b).
• Hypothalamus: Body's thermostat (c); Want center (e); Master hormone regulator (i).
• Cerebellum: Motor coordination (d); Timekeeping (j).
• Thalamus: Emergency center (f).
• Pons: Posture, sleep, swallowing, bladder control (k).
• Corpora Quadrigemina: Visual and auditory reflexes (l).
• Corpus Callosum: Connects cerebral hemispheres (h).
• Lateral Ventricle: Cerebral spinal fluid production (m).

Cerebral Cortex Map

• Lobes: Named based on overlying cranial bones.
  • Frontal (blue)
  • Parietal (yellow)
  • Occipital (pink)
  • Temporal (green)
• Functions are specific to each area.

Frontal Lobe:

• Smell (underside).
• Broca area: Language motor control (left side only).
• Precentral gyrus: Primary motor cortex.

Parietal Lobe:

• Postcentral gyrus: Sensory cortex.
• Somesthetic sensation: Touch, pain, pressure.

Occipital Lobe:

• Visual perception.

Temporal Lobe:

• Auditory cortex: Hearing.
• Wernicke area: Language planning of speech.

Language Centers

Broca area: Motor control of language.
Wernicke area: Plan of speech.
Aphasia: Language impairment.

Types of aphasias:

• Nonfluent (Broca area problem: Motor skills).
• Fluent(Wernicke area: Able to generate sounds but lacks meaning).