Back to AI Flashcard MakerBiology /LGS A-Level OCR Biology - Unit 5 - Plant and Animal Responses Part 3
LGS A-Level OCR Biology - Unit 5 - Plant and Animal Responses Part 3
This deck covers key concepts from Unit 5 of A-Level OCR Biology, focusing on plant and animal responses, including reflex actions, hormone mechanisms, and the fight or flight response.
Reflex reactions
Responds to changes in the environment but not involving the brain; Sensory --> relay --> motor; Brain may be informed but doesn't coordinate; Survival; fast, involuntary and not learned (innate)
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Key Terms
Term
Definition
Reflex reactions
Responds to changes in the environment but not involving the brain; Sensory --> relay --> motor; Brain may be informed but doesn't coordinate; Surviva...
Cranial reflex
Nervous pathway passes through the brain
What makes something an reflex arc
Receptor and effector in same place
Blinking reflex
Cranial reflex; Corneal - object touching eyes; Optical - Light hitting back of eye (retina)
Patnway for corneal blinking reflex
Receptor; Sensory neurone on cornea; Sensory centre on pons; Non-myelinated relay neuron passes action potential to motor neurone; Motor neurone passe...
If the corneal blinking reflex is to be overridden
Sensory neurone on cornea; Myelinated relay neurones inform brain; Allows reflex to be overridden (inhibitory neurone) - faster so reflex can be overr...
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| Term | Definition |
|---|---|
Reflex reactions | Responds to changes in the environment but not involving the brain; Sensory --> relay --> motor; Brain may be informed but doesn't coordinate; Survival; fast, involuntary and not learned (innate) |
Cranial reflex | Nervous pathway passes through the brain |
What makes something an reflex arc | Receptor and effector in same place |
Blinking reflex | Cranial reflex; Corneal - object touching eyes; Optical - Light hitting back of eye (retina) |
Patnway for corneal blinking reflex | Receptor; Sensory neurone on cornea; Sensory centre on pons; Non-myelinated relay neuron passes action potential to motor neurone; Motor neurone passes out of brain to facial muscles |
If the corneal blinking reflex is to be overridden | Sensory neurone on cornea; Myelinated relay neurones inform brain; Allows reflex to be overridden (inhibitory neurone) - faster so reflex can be overridden before it happens |
Knee-jerk reflex | Spinal reflex; Unexpected stretching of quadriceps --> detected by muscle spindles --> causes a reflex reaction (no relay neurone) --> quadriceps contract |
Spinal reflex | Involves the spinal cord rather than the brain |
Muscle spindles | Stretch receptors that detect increase in muscle length |
Class of hormones | Steroid - produced in reproductive organs and adrenal cortex; Peptide - insulin, ADH, adrenaline |
Hypothalamic - anterior axis | Hypothalamus releases hormones (releasing factors); Pass down a portal vessel to anterior pituitary gland; Anterior pituitary gland releases tropic hormones e.g. for thyroid and adrenal |
Tropic hormones | These stimulate other endocrine glands |
Mechanism of steroid hormones | Steroid hormone combines w/ steroid receptor in cytoplasm; Hormone-receptor complex enters nucleus; Complex binds to receptor sites on DNA, activating mRNA transcription; mRNA leaves nucleus; Ribosome translates mRNA into new protein in cytoplasm |
Mechanism of peptide hormones | Adrenaline in the blood binds to membrane bound receptor; Stimulates G-protein to activate Adenyl cyclase; Converts ATP to cAMP; cAMP acts as second messenger by moving into the cell cytoplasm and causing an effect |
Thyroxin | Increases metabolic rate in most cells |
How is thyroxin released | Hypothalamus releases TRH; Travels to anterior pituitary gland and releases TSH; Travels to thyroid through portal vessel and releases thyroxine |
TRH | Thyrotropin releasing hormone |
TSH | Thyroid stimulating hormone |
How are glucocorticoids (cortisol) released | Hypothalamus releases CRH; Travels to anterior pituitary gland and releases ACTH; Travels to adrenal cortex through portal vessel and releases cortisol |
Cortisol | Released as a response to chronic stress | Stimulates breakdown of glycogen |
Coordination of flight or fight | Sensory input; Action potential travels to sensory centres (cerebrum); Signals passed to association areas; If a threat is recognised, cerebrum stimulates hypothalamus; Hypothalamus stimulates sympathetic nervous system and stimulates release of hormones from anterior pituitary gland |
How is the fight or flight response formed | Hypothalamus activates sympathetic nervous system; Impulses activate glands and smooth muscle; Activated adrenal medulla; Secretion of adrenaline into the bloodstream; Hypothalamus also secretes releasing factors e.g. CRH and TRH |
CRH | Corticotropic releasing hormone |
ACTH | Adrenocorticotropic hormone |
Physiological changes in fight or flight response | Pupils dilate - more light enters eyes, retina becomes more sensitive; Heart rate and bp increase; Ventilation depth and rate increases; Less digestion; Blood glucose increases; Metabolic rate increase - faster conversion of glucose to ATP; Endorphins released in brain; Erector pili muscles in the skin contract |
Why do erector pili muscles stand up in fight or flight response | Hairs/ fur stands up - signs of aggression |