Bio 4: Communication and homeostasis Flashcards
Stimulus
Any change in the environment that causes a response
Response
A change in behaviour or physiology as a result of a change in the environment
Good communication system
- Cover the whole body
- Enable specific communication
- Rapid communication
- Short term and long term
Homeostasis
maintenance of the internal environment in a constant state despite external changes
Negative feedback
Process that brings about a reversal of any change in conditions. Ensures the optimum steady state can be maintained, as the internal environment is returned to the original set of conditions after any change.
Positive feedback
Process that increases any change detected by the receptors. Tends to be harmful.
Ectotherm
Organism that relies on external sources of heat to regulate its body temperature
Endotherms
Organism that can use internal sources of heat, such as heat generated from metabolism in the liver, to maintain it’s body temperature
Sweat Glands (response to high temp)
Secrete more sweat onto skin, water in sweat evaporates, using heat from blood to supply latent heat of vaporisation
Hairs on skin (response to high temp)
Hairs lie flat, providing little insulation, thus more heat lost by convection and radiation
Arterioles leading to capillaries in skin (response to high temp)
Vasodilation allows more blood into capillaries near the skin surface; more heat can be radiated from the skin surface
Liver cells (response to high temp)
Rate of metabolism is reduced; less heat generated from exergonic reactions such as respiration
Skeletal muscles (response to high temp)
No spontaneous contractions
Thermoregulatory centre
In the hypothalamus, monitors blood temperature and any changes in core body temperature
Cones and rods
In the eye retina, detect changes in light intensity and wavelengtyh
Olfactory cells
In the nose, detect the presence of volatile chemicals
Taste buds
Detect the presence of soluble chemicals
Pacinian corpuscles
Detect pressure on skin
Sound receptors
Cochlea, detect vibrations in air
Proprioceptors
Detect length of muscle fibres
Transducers
Convert one energy form to another
Polarised membrane
A membrane with a potential difference across it. This is the resting potential
Depolarisation
The loss of polarisation across the membrane. The period when sodium ions entering the cell are making the inside less negative with respect to the outside.
Generator potential
Small depolarisation caused by sodium ions entering the cell
Action potential
Achieved when the membrane is depolarised to a value of about +40mV. The membrane depolarises and reaches a threshold level, sodiums enter and action potential is reached.
Motor neurones
- Action potential from the CNS to an effector
- Cell body in the CNS
- Long axon
- Numerous dendrites
Sensory neurones
- Action potential from sensory receptor to CNS
- Long dendron
- Cell body outside of the CNS
- Short axon
- Numerous dendrites
Resting potential
Potential difference across the cell membrane while at rest. This is about -60mV inside the cell compared with the outside.
Voltage-gated channels
Channels in the cell membrane that allow passage of charged particles or ions. The gate opens and closes, when there is a change in potential difference across the membrane.
Threshold potential
Potential difference of roughly -50mV, the depolarisation has to reach this value for an action potential to be generated
Refractory period
The short period of time after firing during which it is more difficult to stimulate a neurone. Ensures that action potentials are only transmitted in one direction.
Hyperpolarised
When the membrane is more highly polarised than the usual resting state. (More negative than -60mV)
Local currents
Movement of ions along the neurone. The flow of ions is caused by an increase in concentration at one point, which causes diffusion away from the region of higher concentration.
Myelin sheath
Insulating layer of fatty matieral, Sodium and potassium cannot diffuse through. Increases the speed of conduction.
Saltatory conduction
Refers to the ‘jumping conduction’, where the action potential appears to jump from one node of ranvier to the next.
Neurotransmitter
A chemical that diffuses across the cleft of the synapse to transmit a signal to the postsynaptic neurone
Cholinergic synapse
Those that use acetylcholine as their transmitter substance
Synaptic knob
A swelling at the end of the presynaptic neurone. It has many mitochondria for ATP production, large smooth ER, voltage gated calcium channels
Synaptic cleft
Gap between the two neurones.
- 20 nm wide
Post synaptic membrane
-Specialised sodium channels
These have five polypeptides. Two for acetylcholine, with specialised receptors.
Acetylcholinesterase
An enzyme that is in synaptic cleft. It breaks down the transmitter substance acetylcholine. It hydrolyses it to ethanoic acid and choline. This stops the transmission of signals.
Hormones
Molecules released by endocrine glands directly into the blood. They act as messengers, carrying a signal to a specific target organ or tissue. There are two types, steriod and protein or peptide hormones.
Endocrine gland
A gland that secretes hormones directly into the blood. They have no ducts.
Exocrine gland
A gland that secretes molecules into a duct that carries the molecules to where they are used. They do no secrete hormones.
Adenyl cyclase
An enzyme associated with the receptor for many hormones, including adrenaline. It is found on the inside of the cell surface membrane.
Adrenaline.
A hormone released by the adrenal glands medulla. It is an amino acid derivative. Effects include: increased heart rate, increased stroke volume, vasoconstriction, increase mental awareness, dilate pupils, stimulate glycogenolysis
Steroid hormones
- Mineralocorticoids (e.g. aldosterone) help control sodium and potassium levels in blood
- Glucocorticoids (e.g. cortisol) help control the metabolism of carbohydrates and proteins in the liver
Pancreas
Lying below the stomach, it has endocrine and exocrine functions. It has a pancreatic duct which carries fluid to the small intestines. This fluid has amylase, trypsinogen and lipase. It is also alkaline.
Islets of Langerhans: alpha
Manufacture glucagon (hormone), which raises the blood glucose concetration.
+Glycogenolysis
+more fatty acids in respiration
+Gluconeogenesis
Islets of Langerhans: beta
Manufacture insulin (hormone), which lowers the blood glucose concentration \+More glucose enters cell \+Glycogenesis \+Glucose to fats \+More glucose for respiration
Glycogenolysis
Glycogen to Glucose
Gluconeogenesis
Amino acids and fats to Glucose
Glycogenesis
Glucose to Glycogen
Hyperglycaemia
State in which blood glucose concentration is too high
Hypoglycaemia
State in which blood glucose concentration is too low
Diabetes: Type I
Though to result from immune system attacking beta cells, and destroying them. Therefore insulin can no longer be produced, and excess glucose cannot become glycogen (glycogenesis). Normally treated by insulin injections.
Diabetes: Type II
Insulin can still be produced, but the responsiveness to insulin has declined. This could be because the receptors on the liver and muscle cells decline, or the insulin level may decrease. Factors causing early onset: obesity, high sugar diet, family history. Normally treated by lifestyle changes.
Myogenic tissue
Muscle tissue that can initiate its own contractions
Pacemaker
A region of tissue in the right atrium wall that can generate an impulse and initiates the contraction of the chambers
Medulla oblongata
Is found at the base of the brain. The region of the brain that coordinates the unconscious functions of the body such as breathing rate and heart rate
Cardiovascular centre
Specific region of the medulla oblongata that recieves sensory inputs about levels of physical activity, blood carbon dioxide concentrations and blood pressure. It sends nerve impulses to the SAN.
Accelerator nerve
Increases heart rate
Vagus nerve
Decreases heart rate
Heart rates factors
- Movement of limbs
- Exercise
- CO2 concentration
- Adrenaline
- Blood pressure
SAN
Sinoatrial node, region of tissue that can initiate an action potential, which travels as a wave over the atria walls
