Homeostasis and Neuronal Communication Key Terms and Processes Flashcards
Homeostasis
The maintenance of a constant internal environment
Paracrine signalling
When cells communicating with each other secrete chemicals into the environment, which are detected by neighboring cells; the signalling molecule secreted has a complimentary binding site to the glycoprotein on the receiving cell
Why is paracrine signalling not sufficient enough?
Multi cellular organisms need long distance communication systems to operate/synchronise the body’s activities; diffusion distance is simply too far for larger reactions to take place quickly, so another form of communication is needed
Thermoregulation in endotherms
- the heat loss center in the hypothalamus detects the change in core blood temperature
- co ordinates receptors and effectors via the nervous system
Endotherms
Organisms that use metabolic heat to maintain a constant internal temperature, often one different to the environment
Ectotherms
Organisms that do not use metabolic heat to maintain a constant internal temperature, but rather take on the temperature of the environment
Conserving/increasing body temperature
- thermogenesis- increasing metabolic heat production in response to cold environments
- muscle contraction (shivering);
the skeletal muscles contributes the most to heat production, as rate of respiration increases - vasoconstriction;
the arterioles near the surface of the skin constrict, the arteriovenous shunt vessels dilate, so very little blood flows through the capillary networks close to the skin, the skin looks pale and very little radiation takes place as warm blood is kept well below the surface - body hairs stand straight;
the erector pili muscles in the skin contract, pulling the hair or feathers of the animal erect, this traps an insulating layer of air on the skin surface, so less heat is lost by convection or radiation
Reducing body temperature
- increased sweating;
sweat spreads out across the surface of the skin, and evaporates from the surface of the skin, heat is lost, cooling the blood below the surface - panting;
increases airflow, which increases rate of evaporation in the mouth and body - vasodilation;
the arterioles near the surface of the skin dilate when the temperature rises, the atriovenous shunt vessels constrict, this forces blood through the capillary networks close to the surface of the skin, the skin flushes and cools as a result of increased radiation
Negative feedback
small fluctuations a factor away from an ideal set point are detected by receptor cells, a response is triggered to bring the factor back to the set point
Positive feedback
a derivation from the set level causes a more amplified derivations away from the set level
Central Nervous System
brain and spinal cord together
Peripheral Nervous System
motor neurones and sensory neurones outside of the spinal cord
Somatic Nervous System
- branch of the peripheral nervous system
- under conscious control, has input from the sensory neurones and has output to motor neurones going to effectors
Autonomic Nervous System
- branch of the peripheral nervous system
- not under conscious control, regulates involuntary smooth muscle contraction (in blood vessels and intestines), cardiac muscle contraction, gland secretion of hormones
- Noradrenaline neurotransmitter at the NMJ and effector
Sympathetic Nervous System
- branch of the autonomic nervous system
- causes an increase in activity, preparing for action eg: increasing heart rate, decrease in peristalsis, reduced saliva production
- Noradrenaline neurotransmitter at the NMJ
Parasympathetic Nervous System
- branch of the autonomic nervous system
- causes a decrease in activity, when relaxed eg;
a decrease in heart rate, increase in digestion, increased saliva production - Acetylcholine is the neurotransmitter at the NMJ
A nerve is a …
… bundle of neurones surrounded by fibrous tissue
Neurones are …
… specialised cells that transmit nerve impulses over long distances
Schwann cells are …
… a type of glial cell, which provide support, insulation and produce myelin for insulation (for any myelinated neurones)
Cell bodies of sensory neurones are in …
… swellings called ganglia situated just outside the spinal cord
Cell bodies of motor neurones are in …
… inside the spinal cord
Some motor neurones in the autonomic NS have their cell body outside the …
… ganglia
Transduction
the conversion of types of energy into one form
eg; light/sound -> electrochemical of a nerve impulse
Type of sensory receptor: Pacinian corpuscle
a) specific stimulus?
b) sense organ?
a) mechanical pressure
b) deep in skin (soles of feet/fingers)
Type of sensory receptor: Chemoreceptors
a) specific stimulus?
b) sense organ?
a) chemicals
b) respiratory centre at the base of the brain/nose
Type of sensory receptor: Thermoreceptor
a) specific stimulus?
b) sense organ?
a) temperature changes
b) skin
Type of sensory receptor: Hair cell
a) specific stimulus?
b) sense organ?
a) sound
b) ear (cochlea)
Type of sensory receptor: Baroreceptor
a) specific stimulus?
b) sense organ?
a) pressure changes in the arterial wall
b) heart - blood vessels
Type of sensory receptor: Photoreceptor
a) specific stimulus?
b) sense organ?
a) changes in light intensity
b) eyes
Structure and function of the:
Cell body
- contains the nucleus, endoplasmic reticulum and many mitochondria
Structure and function of the:
Myelin Sheath
- formed by Schwann cells
- wrapped around the axon
- insulates electrical impulses allowing faster transmission
Structure and function of the:
Dendron
- conducts electrical impulses towards the cell body in a sensory neuron
Structure and function of the:
Axon
- leads away from the cell body in a sensory and motor neuron
Structure and function of the:
Dendrites
- connects neurones via synapses to other neurones
Structure and function of the:
Node of Ranvier
- small gap in myelin sheath
- Na+ and K+ voltage-gated channel proteins are found
Structure and function of the:
Axoplasm
- cytoplasm in the axon
Resting Membrane Potential
- sodium ions are actively transported across the axon membrane
- the phospholipid bilayer prevents the sodium ions
