Lecture 5 Flashcards
(54 cards)
Where do pain fibers end?
In periaqueductal grey matter or periventricular nuclei
Periaqueductal grey matter or periventricular nuclei stimulate neurons that secrete __.
Enkephalins
Pain fibers synapse with:
Raphe magnus or paragigantocellularis nucleus
What are the causes of visceral pain?
1) Ischemia: Decrease or low blood flow to the tissue = tissue damage =
releases chemicals that excite the free nerve endings of pain receptors
2) Chemical irritation from perforated peptic ulcer, or acids from the biliary system
= irritates the viscera and peritoneum
3) Spasm of a hollow viscus = constriction or contraction of SI (intestinal
colic) = mechanical stimulation of the free nerve endings as they press on the
free nerve endings
4. Overdistension of a hollow viscus = increase the pressure on the walls of
the organs.
Cold receptors respond from -°C with a peak response at _°C.
7-44; 25
Warm receptors respond from -°C with a peak response at _°C, which can cause pain.
30-49; 44
What determines temperature sensation?
The relative degree of stimulation of the receptors
What are the 4 different receptors?
1) Warm
2) Cold
3) Burning hot
4) Freezing cold.
Can thermal receptors adapt to the stimulus?
Yes, but not completely
What does cold or warm temperature do?
Change the metabolic rate of the receptor = changes the rate of intracellular reaction (how?) By changing the permeability of
ions in the receptors, and the receptor potential = Change the action potential formed in the afferent neuron connected to these receptors.
If you increase the temperature from 15 to 20 °C:
The number of impulses
increases to around the level of 25°C (person feels too hot)
If a person stays under an increased temperature for a while, what happens?
There is a slight decrease in the number of impulses and the heat doesn’t feel as
intense or hot.
What is thermal adaptation?
It starts as fast adaptation then slow adaptation, but there is no complete adaptation to temperature
What are the 3 layers of the eye?
1) Sclera
2) Choroid
3) Retina
What surrounds 4/5 of
the eyeball? What about the last 1/5?
The sclera; The cornea (anteriorly)
What is the sclera made up of?
Very dense connective tissue
What determines whether one can undergo laser surgery or not?
The cornea
What is the choroid?
A vascular component of the eye which continues anteriorly with the ciliary body
Which muscle is part of the choroid? What does it continue as?
Ciliary muscle; continues anteriorly as the iris
What connects the ciliary body and the lens’ capsule? What is its function?
Suspensory ligaments, which (through the work of the ciliary muscle) change the shape of the lens.
What is the lens made up of?
Multiple layers of protein
What allows the lens to change shape? What are its shapes?
its flexibility; flatter (less convex) and fatter (more convex)
The __ divides the eyeball into 2 cavities:
Lens;
1) Anterior cavity: Between the lens and cornea
2) Posterior cavity: Extends behind to the retina
The 2 cavities of the eyeball are connected by the:
Pupil
