reflex actions + fight or flight response Flashcards
What is a reflex? (1)
An involuntary response to a sensory stimulus
Why are reflexes essential for survival? (3)
Involuntary:
The brain’s decision-making regions are not involved, allowing the brain to focus on more complex responses;
Present at birth: Provides immediate protection;
Extremely fast: Involves 1 or 2 synapses, leading to rapid responses.
What is a reflex arc, and what are its components? (5)
The pathway of neurones involved in a reflex action;
Receptor detects the stimulus and creates an action potential in the sensory neurone;
The sensory neurone carries the impulse to the spinal cord;
The relay neurone connects the sensory neurone to the motor neurone;
Motor neurone carries the impulse to the effector for the appropriate response
What is the function of the blinking reflex? (1)
Quickly closes the eyelids to prevent damage to the eye
How does the blinking reflex work? (5)
- Sensory nerve endings in the cornea are stimulated by touch;
- The nerve impulse travels along the sensory neurone to a relay neurone in the CNS;
- The impulse is passed from the relay neurone to the motor neurones;
- The motor neurones send impulses to the orbicularis oculi muscles (eye muscles);
- Causing them to contract and close the eyelids
How is the blinking reflex used in clinical assessment? (2)
Indicates that the lower brain stem is functioning;
Helping to determine if a patient is brain-dead
What is the function of the knee-jerk reflex? (1)
Helps to maintain posture and balance
How does the knee-jerk reflex work? (4)
- Stretching of the patellar tendon acts as a stimulus;
- This initiates a reflex arc that causes the extensor muscle on the top of the thigh to contract;
- A relay neurone inhibits the motor neurone of the flexor muscle, causing it to relax;
- This results in the leg kicking
What does the absence of the knee-jerk reflex indicate? (1)
Nervous system problems
What triggers the fight or flight response in organisms? (3)
- When an organism is threatened;
- Sensory neurones send nerve impulses to the hypothalamus;
- Which activates both the hormonal system and the sympathetic nervous system
How is the hormonal system activated during the fight or flight response? (2)
- The adrenal-cortical system is activated, and the pituitary gland releases ACTH;
- Which stimulates the adrenal cortex to release steroidal hormones
How does the sympathetic nervous system contribute to the fight or flight response? (3)
- It triggers the release of adrenaline from the adrenal medulla;
- Which causes various physiological changes;
- Like increased heart rate, dilation of pupils, deeper breathing, and glycogen breakdown
What physiological changes occur during the fight or flight response due to adrenaline? (6)
- Heart rate increases as blood is pumped faster;
- Pupils dilate to take in more light for better vision;
- Airways relax so breathing becomes deeper to allow more oxygen into the lungs;
- Glycogen is converted to glucose so that more glucose is available for muscle respiration;
- Blood is diverted from the skin and gut to the heart, lungs, and muscles for emergency functions;
- Erector pili muscles contract so hair stands up to make the animal appear larger
What is the role of first messengers and second messengers in cell signalling? (2)
First messengers (e.g., hormones) = carry chemical messages from the endocrine gland to a receptor on the target cell;
Second messengers = relay signals within the cell and trigger changes in the cell’s function, often via a cascade of reactions
How does adrenaline activate glycogen breakdown in liver cells? (4)
Adrenaline binds to receptors on liver cells, activating adenylyl cyclase;
Which converts ATP to cyclic AMP (cAMP), the second messenger;
cAMP triggers a cascade of reactions;
That results in the breakdown of glycogen to glucose
