Ch 15 Homeostasis Flashcards
Negative Feedback system
a small change in one direction is detected by sensory receptors. Effectors work to Reverse the Change and restore conditions
Positive Feedback System
a Change in the internal environment of the body is Detected by Sensory Receptors, and Effectors are stimulated to Reinforce that Change, Increasing the Response.
Ectotherm
“outside heat”
core body temperature is heaviliy dependent on the external environment.
use Behavioural Responses to control body temperature.
Endotherms
“inside heat”
organism relies on metabolic processes to maintain a very stable core body temperature, regardless of the environment.
Temperature Regulation in Ectotherms
Behavioural Responses:
Bask in sun / Seek shade
orientate body to increase SA exposed
Conduction - press body against warm/cool ground
Maximise/Minimise movement to increase/decrease metabolic heat generated.
Temperature Regulation in Ectotherms
Physiological Responses:
Dark colours absorb more radiation than light colours
Alter heart rate to alter metabolic rate
Where are Temperature Receptors in Endotherms found?
Peripheral temperature recptors are in the Skin - detect changes in surface temperature. (pre-empt & therefore prevent change in blood temperature)
Temperature Receptors in the Hypothalamus - detect temperature of the blood deep in the body
Cooling Down in Endotherms:
Vasodilation
arterioles near skin surface dilate when temp. rises, forcing the blood through the capillary networks at the surface of the skin = skin flushes and cools as a result of increased radiation.
Sweating
rate of sweating increases when core temperature increases. As Sweat Evaporates from the skin surface, heat is lost, cooling the blood bellow.
Erector Pili Muscles Relax
= hair lies flat to avoid trapping insulating layer of air
Warming Up in Endotherms:
Vasoconstriction
arterioles near skin surface constrict when temp. falls, so little blood flows through the capillary networks at the surface of the skin = skin looks pale and little radiation takes place. Warm blood is kept well bellow the surafce
Decreased Sweating
rate of sweating decreases/stops as core temperature falls.
Erector Pili Muscles Contract
= Hair/Feathers erect, trapping an insulating layer of air close to skin.
Shivering
= rapid involuntary contracting and relaxing of voluntary muscles. Metabolic heat is produced to raise the core temperature.
Temperature Regulation in Endotherms
Anatomical Adaptations:
minimise/maximise surafce are to volume ratio to increase/decrease cooling, e.g. small or large ear.
Thick layer of insulating fat/blubber bellow skin
Controlling Thermoregulation:
Heat Loss Centre & Heat Gain Centre
Interaction of Sensory Receptors, Autonomic nervous system, and Effectors in skin & muscles enables Endotherms to maintain a stable core body temperature.
Heat Loss Centre -
activated when Temperature of Blood flowing through Hpothalamus Increases.
Sends impulses through Autonomic Motor Neurones to Effectors in skin & muscles, Triggering Responses to Lower Core Temperature (Cool Down)
Heat Gain Centre -
activated when Temperature of Blood flowing through Hypothalamuc Decreases.
Sends Impulses through Autonomic Motor Neurones to Effectors in skin & muscles, Triggering Responses to Raise Core Temperature (Warm Up)
Excretion in Mammal; Main Waste Products:
Carbon Dioxide - waste from cellular respiration, excreted by exhalation out Lungs
Bile Pigments - formed in Liver from Breakdown of Haemoglobin from old red blood cells. Excreted in Bile from Liver into Small Intestine via Gall Bladder & Bile Duct
Nitrogenous Waste Products (Urea) - Formed in Liver from Breakdown of Excess Amino Acids. Urea is Excreted by the Kidneys in the Urine
The Liver
Functions:
Reddish-Brown (blood) organ, 5% total body mass
Made of several Lobes
>Hepatic Artery & Hepatic Portal Vein (mix in sinusoids)
Structure of the Liver
Hepatocytes -
large nuclei prominant Golgi Apparatus & Lots of Mitochondria
secrete Bile into Canaliculi
Sinusoids = where blood mixes
surrounded by hepatocytes
Kupfer Cells = resident Macrophages, prevent disease
Liver : Carbohydrate Metabolism
Blood glucose levels Rise = Insulin levels rise = Hepatocytes convert Glucose into Glycogen (Glycogenesis)
Blood glucose levels Fall = Glucagon levels rise = Hepatocytes convert Glycogen to Glucose (Glycogenolysis)
Liver : Deamination of Excess Amino Acids
Deamination = removal of amine group.
convert amino acid into Ammonia (toxic), then to Urea (less toxic), excreted by kidneys
remainder of amino acid fed into cellular respiration or stored as lipid
Ammonia - Urea in Ornithine Cycle; set of enzyme-controlled reactions.
Transamination = conversion of one amino acid into another; important as overcomes problem that diet doesnt always contain required balance of amino acids
Liver : Detoxification
& examples
Liver processes toxins, making them harmless Hydrogen peroxide (catalase) = oxygen and water Ethanol (alcohol dehydrogenase) = ethanal = ethanoate
The Kidneys
Cortex = dark outter layer (capillaries) surrounded by Capsule
Medulla = contains nephron tubules
Pelvis = central chamber where urine collects
>Renal Artery
Functional units of the Kidney
Nephrons
blood is filtered = Ultrafiltration
most filtered material returns to blood = Selective Reabsorbtion
Bowman’s Capsule contains Glomerulus - ultrafiltration
Proximal Convoluted Tubule - selective reabsorbtion
Loop of Henle (Descending & Ascending)
Distal Convoluted Tubule - fine tunes salt/water balance
Collecting Duct - fine tuning of salt/water balance (ADH)
Process and Structures involved in Ultrafiltration
Relatively wider Afferent arteriole from renal artery supplies blood to glomerulus. Blood leave via narrow Efferent arteriole = Pressue in Arterioles, Forcing blood Out through Capillary Walls (sieve)
Fluid passes through Basement Membrane (network of collagen fibres & other proteins = 2nd sieve)
Podocytes with pedicels (extensions wrap around capillaries forming slits)
Filtrate: glucose, salt, water, urea in same concentrations as blood plasma
Selective Reabsorbtion:
water, glucose, salts and other useful substances are returned from filtrate back to blood.
PCT - Glucose, Amino acids, Vitamins & Hormones actively transported back to blood
Sodium ions are actively transported to blood and Chloride ions and Water passively follow down conc gradients.
PCT cells; Microvili increase SA for reabsortion and have many Mitochondira (ATP for active transport)
What is the Loop of Henle?
Acts as a Countercurrent Multiplier, using Energy to produce Conc Gradients that Result in Movement of substances such as Water. Ions are actively transported and this produces a Diffusion Gradient in the Medulla.
What happens in the Descending Limb of the Loop of Henle?
Filtrate entering is Isotonic with blood
Water diffuses out the filtrate Down W.P gradient by Osmosis.
Upper part is impermeable to water
Lower part is permeable to water
Not permeasble to ions; no active transport
Na+ and Cl- ion concentration in tissue fluid increases in the medulla due to actuvity of the ascending limb.
Fluid reaching hairpin bend is very concentrated and is Hypertonic to the blood in capillaries
What happens in the Ascending Limb of the Loop of Henle?
Permeable to Sodium and Chloride ions; Diffuse out Filtrate into blood, Down Concentration gradient.
2nd section of Ascending Limb, Na and Cl ions are actively transported out the filtrate, against a conc gradient. = high concentration of Na and Cl ions in medulla tissue fluid (Essential to Countercurrent Multiplier System)
Impermeable to water (water cannot leave filtrate, so fluid becomes dilute)
fluid at top of Ascending Limb is Hypertonic to blood
