Week 1 Flashcards
3 layers of skin
Epidermis, Dermis, Subcutaneous Tissue
Skin Types
Glaborous and Hairy
Glaborous Skin -where found? -receptors?
-without hair -Ventral surface of fingers, palm of hand, pads of toes, sole of foot, ear lobes, external genetalia -dense collection of somatosensory receptors; Meissener corpuscles, Merkels discs, ruffini nerve endings, pacinian corpuscles, free nerve endings
Hairy Skin -where found -receptors?
-hair protruding from hair folllicles; density varies -where glaborous skin does not occur -hair follicles have free nerve endings around base, sense movement -meissner corpuscles sparse/absent; merkels cells less dense; pacinian corpuscles in subcutaneous layer
3 types of receptors
Mechanoreceptors (touch, pressure, vibration, hair movement); Thermoreceptors (skin temp); Nociceptors (pain)
Mechano receptors -function -types (5)
-respond to an object that comes in contact with skin and causes deformation (touch, pressure, vibration, hair movement) -Ex: meissner corpuscle, merkel disk, ruffini endings, pacinian corpuscle, hair follicle
Thermoreceptor -function -kinds (2) -nerves
-identifies changes in skin temperature -warmth: small unmyelinated nerve fibers increase action potential with increasing skin temp between 30C and 45C ; cold:small myelinated and unmyelinated fibers increase action potential with decreasing temperature between 43C and 25C -free nerve endings in both epidermis and dermis
Nociceptors -function -types (4) -nerves
-response to changes in the immediate environment of the nerve endings that are due to stimuli that are about to cause/causing tissue damage/inflammatory responses -chemical: secretions associated with inflammation; thermal: extremes of temperature (above 45C and lower than 20C); mechanical: extreme pressure; polymodal: responds to 2 of the 3 above -free nerve endings in dermis and epidermis
Nerve pathway for mechano receptors
-sensory information received, travel to spinal cord and up dorsal column -primary synapse at medulla, where signal crosses over and continues to travel up though medial lemniscus -secondary synapse at thalamus -tertiary synapse at post central gyrus in the primary somatosensory cortex
Nerve pathway for thermoreceptor/nociceptors
-primary synapse at dorsal horn where it crosses over -travels up ventrolateral spinothalamic tract -second synapse at VPL of thalamus -third synapse at post central gyrus (somatosensory cortex)
If injury occurs in right dorsal column T5-T7 what is affected?
-dorsal column contains mechanoreceptor tract (fine touch), since it is tract, sensation of fine touch will be decreased on right side from T5 down.
If injury occurs to left dorsal root ganglion at T10 what is affected?
-all senses are affected fine touch, curde touch, pain, and temp -the decrease in sensation will only be felt on the right side in the T10 zone (dermatome), because injury occurs in ganglion instead of tract
If injury occurs to right side of medulla oblongata damaging the ventrolateral tract what is affected?
-Decrease in crude touch, temp, pain perception to left side (contralateral) of the body which will include hand and foot
Sweat glands -function -structure
-secrete sweat to control body temp -2 parts; coiled cell (contains sympathetic nerve innervation and iso-osmotic fluid), duct cell (impermeable to water, but allows for reabsorption of Na and Cl in interstitum creating hypo-osmotic fluid)
What controls sweat gland?
-Sympathetic innervation (SPECIAL) because it only responds to ACH instead of Epi and is a muscarinic receptor instead of adrenergic
What type of fluid does a sweat gland release? Why?
Hypo-osmotic, because the ductal part of the sweat gland in impermeable to water, trapping it in the duct but allowing for ions to transfer back into the interstitium, reducing the amount of solute in the water being released from gland.
Importance of hypo-osmotic secretion
In patients that have been sweating a lot, you will commonly see that their plasma is hyperosmotic because the solute from the sweat is being re-absorbed with the body while the water is being released through the gland creating a high solute concentration in the body
What part of nervous system controls blood flow in the skin?
sympathetic nervous system; can dilate or contract
Decrease in sympathetic stimulation causes
reduced NE resulting in Vaso-dilation
Increase in sympathetic stimulation causes
increased NE resulting in Vaso-constriction
What causes vasodilation?
elevation in core temp (caused by hot environment, exercise, etc); allowing for increase of blood at skin surface, allows for release of heat to environment
How is personhood affected by illness?
When a person is ill their life style will be affected; ex. pain experienced from shingles could cause decrease in ability to do work
What is normal set point temperature for the body?
98.6F or 37C
What determines core body temp?
-Heat gained -Heat lost to environment
How is heat gained?
-Metabolism and muscle shivering
How is heat lost to environment
-convection/conduction: related to skin temp and temp of air -radiation: related to skin temp and temp of objects around skin -evaporation:
How does core temperature change?
There is disturbance in balance between heat lost and heat gained
How does body regulate system to minimize changes in core temperature?
-has to offset disruption in balance before a big change is noticed by the body -ex: increase in heat lost; need to increase heat gained through shivering
Mechanisms used to regulate change in core body temp
-vasodilation/ constriction -muscle shivering -sweat
What controls mechanisms used to regulate change in core temp?
Preoptic anterior hypothalamus
What does the pre-optic anterior hypothalamus compare core body temp to?
set point temperature
Can set point differ? Why?
Yes, during times of illness the body will increase the set point temperature to induce a fever and to aid in fighting off infection
How is fever induced?
Cytokines; IL-1, TNF alpha, IL-6
How does pre-optic anterior hypothalamus know what core temperature is in the body?
Tc Sensors-thermo receptors
Influence of hot environment on Tc? Why?
Reduction in loss of heat to environment, because environment is hotter than you are
Thermoregulatory response to exposure to heat? -causes -end result
-sweating, vasodilation -caused by decrease in sympathetic innervation with NE causing vasodilation and ACH causing sweating
Role of skin temperature with heat
-signals behavioral response–go into AC or shade -lowers threshold for sweat response–makes it easier to sweat by lowering amount of heat needed to trigger sweat response
Influence of cold environment on Tc? Why?
Increase in heat lost to environment because the environment is colder than you are
Thermoregulatory responses to cold environment -caused by? -end goal?
-shivering and vasoconstriction -sympathetics? -decrease amount of heat lost to environment while simultaneously increasing the amount of heat generated by body
Role of skin temperature with cold?
Decrease in skin temperature raises threshold for activating shivering
Influence of exercise on Tc? Why?
Increase in Tc because increase in metabolism
Thermoregulatory responses to exercises? -Causes? -End goal?
-Vasodilation and sweating -Increase in sympathetics -Increase amount of heat lost to environment
Tc in response to dehydration
Core temp will rise with dehydration because ECF will become hyperosmotic. This means there is not enough water to release sweat and decrease in fluid from ECF will cause vasoconstriction to help with blood pressure.
What does an increase in set point do to core temp?
Will make body think you’re cold so there will be a rise in core temperature.
Thermoregulatory response to cytokines -phases-causes
-chill phase: will raise set temperature, make body shiver and vasoconstrict; due to influx of cytokines -deferverscent phase: will lover set temp back to normal, cause you to sweat and vasodilate; due to decrease in cytokines