2- homeostasis Flashcards
(40 cards)
Q: What is homeostasis?
A: The regulation of internal conditions (e.g. temperature, pH, glucose levels, water content) to maintain optimum conditions for enzyme action and cell function.
Q: Why is homeostasis important?
A: It maintains stable conditions for cell activity and survival. Even small deviations can affect enzyme function or be fatal.
Q: What two systems are used for homeostasis communication?
A: The nervous system (fast, electrical impulses) and the endocrine system (slower, chemical hormones).
Q: What monitors and regulates body temperature?
A: The thermoregulatory centre in the brain and temperature receptors in the skin.
Q: What is vasodilation and how does it cool the body?
A: Arterioles widen → more blood to skin capillaries → more heat lost via radiation.
Q: What is vasoconstriction and how does it reduce heat loss?
A: Arterioles narrow → less blood near skin surface → less heat lost.
Q: What other mechanisms help regulate temperature?
A:
Sweating (cooling by evaporation)
Shivering (muscle contractions produce heat)
Hair erection (insulates or allows heat loss depending on position)
Q: What organ regulates water content in humans?
A: The kidneys.
Q: How is water content adjusted?
A:
Too much water → less reabsorbed in kidneys → dilute urine
Too little water → more reabsorbed → concentrated urine
Q: What hormone controls water balance?
A: ADH (antidiuretic hormone) – increases water reabsorption in kidneys.
Q: What are the two main parts of the nervous system?
A:
CNS (Central Nervous System): brain and spinal cord
PNS (Peripheral Nervous System): all other nerves
Q: What is the nervous system’s function?
A: Rapid communication via electrical impulses to coordinate responses to stimuli.
Q: What is the typical nerve signal pathway?
A: Stimulus → Sensory neurone → Relay neurone → Motor neurone → Effector → Response
Q: What is a synapse?
A: The gap between two neurones where neurotransmitters transfer signals.
Q: How is a nerve impulse transmitted across a synapse?
A: Electrical impulse triggers release of neurotransmitters → cross synaptic cleft → bind to receptors on next neurone → new electrical impulse.
Q: Why do impulses travel in one direction only?
A: Only presynaptic neurones release neurotransmitters, and postsynaptic neurones have receptors.
Q: Example pathway of a reflex?
A: Stimulus (e.g. pin) → Receptor → Sensory neurone → Relay neurone (spinal cord) → Motor neurone → Effector (muscle) → Response
Q: What is a reflex arc?
A: A rapid, automatic response to a stimulus that bypasses the conscious brain.
Q: What are the key structures of the eye and their functions?
Cornea: refracts light
Iris: controls pupil size
Lens: focuses light on retina
Retina: contains rods (light) and cones (color)
Optic nerve: sends impulses to brain
Ciliary muscle & Suspensory ligaments: adjust lens shape
Q: How does the eye focus on near vs. far objects?
Near: ciliary muscles contract, lens thickens → more refraction
Far: ciliary muscles relax, lens thins → less refraction
Q: What is the pupil reflex?
A: In bright light: pupil constricts; in dim light: pupil dilates.
Q: What is a tropism?
A: A directional growth response to a stimulus.
Q: Types of plant tropisms?
Phototropism: response to light
Geotropism: response to gravity
Q: How do auxins affect tropisms?
\A:
Accumulate on shaded side of shoots → cells elongate → shoot bends toward light.
In roots, auxin inhibits elongation, so growth bends downward.
