Spinal Cord
Sensory + Reflex
Endocrine
Bone + Thermoregulation
100

What are the three direction white matter runs in?

  • Ascending: up to higher centers (sensory inputs)
  • Descending: from brain to cord or lower cord levels (motor outputs)
  • Transverse: from one side to other (commissural fibers)
100

BLANK receptors are activated by heat and capsaicin

vanilloid receptors

100

What are water- and lipid-soluble hormones?

  • Water-soluble hormones (all amino acid-based hormones except for thyroid hormone) act on receptors in the plasma membrane.
  • Lipid-soluble hormones (steroid and thyroid hormones) act on intracellular receptors.
100

What are the hormones which control calcium balance?

The 3 hormones responsible for Ca2+ regulation are: parathyroid hormone (PTH), calcitriol (vitamin D3), and calcitonin

200

What order neuron has axons that extend to thalamus or cerebellum?

second-order neuron

200

Distinguish between fast and slow pain.

  • Fast pain: Sharp and localized carried by A-delta fibres
  • Slow pain: Dull and diffuse carried by C fibres
200

What is up vs down regulation.

  • Up-regulation: Generation of more hormone receptors on a cellular surface – often caused by low levels of the hormone.
  • Down-regulation: A reduction in the number of receptors in the presence of high hormonal levels that persist over time – often caused by prolonged exposure to high hormone levels.
200

What are the organic components of bone?

The organic components include:

  • Osteoblasts (immature) and Osteocytes (mature) are bone-forming cells
  • Osteoclasts – large cells that resorb or break down bone matrix (more on cells later)
  • Osteoid – unmineralized bone matrix composed of proteoglycans, glycoproteins, and collagen.
300

Somatosensory signals travel along three main pathways on each side of the spinal cord, name the three ascending pathways.

  • Dorsal column–medial lemniscal pathways
  • Spinothalamic pathways
  • spinocerebellar tracts
300

What is a flexion reflex and give an example?

Flexion reflexes are polysynaptic reflex pathways that cause an arm or leg to be pulled away from noxious stimuli

They rely on divergent pathways in spinal cord

A painful stimulus can activate multiple excitatory and inhibitory interneurons in spinal cord

In the affected limb, flexors are activated and extensors inhibited

In the opposite limb, extensors are activated and flexors are inhibited.

For example: step on something sharp, other limb will be activated to give balance and not fall over


300

The steps of the cAMP second messenger

  • Step 1: Hormone binds to receptor
  • Step 2: The receptor changes shape → G protein binds to the receptor → the guanosine diphosphate (GDP) bound to the G protein is displaced by a high-energy GTP. It is now “on”
  • Step 3: The now active G protein moves and binds to its effector – adenylate cyclase.
  • At this point GTPase cleaves off a Pi from GTP leaving GDP bound to G protein (the G protein is now inactive and free to roam)
  • Step 4: The now activated adenylate cyclase generates cyclic AMP (cAMP). This process requires energy (ATP). cAMP is the intracellular second messenger
  • Step 5: cAMP diffuses through the cell triggering a number of chemical reactions typically involving protein kinases (enzymes).
300

Distinguish between heat exhaustion and heat stroke.

Heat Exhaustion

  • Heat-associated collapse after vigorous exercise, evidenced by elevated body temperature, mental confusion, pale complexion, and fainting
  • Primarily due to dehydration and low blood pressure
  • Body temperature is between 37.5 and 39º C but heat-loss mechanisms are fully functional.


Heat stroke

  • Heat exhaustion can progress to heat stroke if the body is not cooled and re-hydrated
  • The skin is flushed and dry
  • Immediate and rapid cooling is necessary because enzymes begin to denature at 41º C.
400

What are direct (pyramidal) pathways?

Impulses from pyramidal neurons in precentral gyri pass through pyramidal (lateral and ventral corticospinal) tracts. 

Descend directly without synapsing until axon reaches end of tract in spinal cord.

In spinal cord, axons synapse with interneurons (lateral tract) or ventral horn motor neurons (ventral tract).

Direct pathway regulates fast and fine (skilled) movements.


400

What are otoliths and how do they detect movement?

  • The sensory structure for the utricle and saccule are called the maculae
  • The maculae are composed of hair cells embedded within another gelatinous mass (otolith membrane) topped with calcium carbonate and protein particles called otoliths
  • Gravity or linear acceleration can cause the otoliths to move and the otolith membrane moves with them
  • This bends the hair cells embedded within the otolith membrane.
400

Explain the PIP-calcium pathway.

  • Step 1: Hormones lock into place and the receptor changes shape (same)
  • Step 2: Binding of inactive G protein to the receptor occurs → G protein becomes “active” as GTP displaces GDP (same)
  • Step 3: The G protein binds to and activates membrane bound phospholipase C (the effector enzyme) – the G protein then becomes inactive
  • Step 4: Phospholipase C (enzyme) splits a plasma membrane phospholipid (PIP2 – phosphatidyl inositol biphosphate ) into 2 second messengers: DAG (diacylglycerol) IP3 (inositol triphosphate)
  • Step 5: DAG activates specific protein kinases (e.g. protein kinase C) IP3 triggers the release of Ca2+ from the endoplasmic reticulum and other sites. 
  • Step 6: Free Ca2+ acts as a second (or technically third) messenger by:
    • Altering activity of enzymes and plasma membrane Ca2+ channels
    • Binding to calmodulin
    • Once calmodulin is activated, enzymatic activity increases and cellular responses are amplified.
400

Name the four heat output and the description of each.

Radiant: Heat loss via infrared or other wavelengths -  accounts for almost half of bodily heat loss

Conductive: Heat loss through contact with another object (e.g. pumping gas in winter)

Convective: Heat carried away from the body by air that is warmed

Evaporative: Heat lost in evaporated water (e.g. sweat, respiratory tract).


500

What is a lumbar puncture (spinal tap)?

A lumbar puncture (spinal tap) is a test used to diagnose certain health conditions. It's performed in your lower back, in the lumbar region. During a lumbar puncture, a needle is inserted into the space between two lumbar vertebrae to remove a sample of cerebrospinal fluid.

500

What is alpha-gamma co-activation?

  • when alpha motor neurons fire during normal voluntary activation of a muscle: as extrafusal muscle fibres shorten, so would intrafusal fibres… 
  • This would cause tension to decrease in the muscle spindle thereby deactivating it.
  • To correct for this lack of activation in the spindle, gamma motor neurons are co-activated along with alpha motor neurons
  • Gamma motor neurons cause intrafusal fibres to contract at the same time extrafusal fibres contract 
  • As a result, the spindle remains active even though the extrafusal muscle is contracting.

500
Posterior Pituitary vs Anterior Pituitary 

POSTERIOR 

  • Derived developmentally from a down-growth of neural tissue.
  • PP maintains a neural connection with hypothalamus through infundibulum via a nerve bundle called the hypothalamic-hypophyseal tract. 
  • This tract is comprised of axons from neurons in the supraoptic and paraventricular nuclei of hypothalamus.
  • These neurons manufacture and transport oxytocin (paraventricular n.) and antidiuretic hormone (supraoptic n.).
  • When these neurons fire, they release these 2 hormones into a capillary bed in the PP.

ANTERIOR

  • Originates developmentally from the oral mucosa (epithelial tissue).
  • There is no direct neural connection between the anterior pituitary and the hypothalamus.  
  • There is a vascular connection.
  • Releasing and inhibiting factors are secreted by the ventral hypothalamus into the primary capillary plexus.
  • These substances flow from the primary to the secondary capillary plexus via the hypophyseal portal system and cause the release of other hormones via the vascular system.
    • The six hormones of the adenohypophysis:
    • Are abbreviated as GH, TSH, ACTH, FSH, LH, and PRL.
500

What is Wolff's law? (Hint: four components)

Wolff’s law – a bone grows or is remodeled in response to the forces or demands placed upon it:

1. Long bones are thickest midway along the shaft (where bending stress is greatest)

2. Curved bones are thickest where they are most likely to buckle

3. Trabeculae form along lines of stress

4. Large, bony projections occur where heavy, active muscles attach.

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