B10- The human nervous system Flashcards
Homeostasis
Regulation of a cell’s internal conditions to maintain optimum conditions in response to internal or external changes
3 internal conditions
Body temperature, water content, blood glucose concentration
Examples of external changes and their effect
Exercising- decreases blood sugar, decreases water content
Temperature- increases/decreases body temperature
Examples of internal changes and their effect
Food- increases blood sugar
Drinking-increases water content
Stimuli
Changes in the internal or external environment
2 types of automatic control systems
Nervous system, endocrine system
3 key features of a control system and brief description
Receptor- detects stimuli
Coordination centre- receives and processes info
Effector- muscles or glands that bring responses
Negative feedback loop
Receptor detects stimuli, coordination centre sends effector to respond, bring back to optimum
Optimal temperature for human enzymes
37oc
Hypothalamus contains?
Receptors sensitive to blood temperature
How the body responds to being too cold?
Shivering–> muscles contract–> respiration increases–>generates heat
Vasoconstriction–> blood vessels narrow–> decreases flow–> less heat radiated out of blood
How the body responds to being too hot?
Sweating–> water evaporates–>energy to environment
Vasodilation–> blood vessels widen–> increases flow–> more heat radiated out of blood
How the body responds to blood glucose being too high?
Pancreas releases insulin–> glucose moves from blood to cells–> stored as glycogen–> excess stored as lipids
How the body responds to blood glucose being too low?
Pancreas releases glucagon–> glycogen converted back to glucose–> then released into blood
Nervous system
Network of neurones bundled into nerves which carry electrical impulses in reaction to stimuli
Two parts of the nervous system
Central nervous system (CNS)–> brain and spinal chord
Peripheral nervous system (PNS)–> rest of nerves in body
Pathway from stimulus to response?
What is it also known as?
Stimulus–> receptor–> sensory neuron–> relay neuron (CNS)–> motor neuron–> effector–> response
Reflex arc
What are effectors?
Muscles or glands that contract or secrete substances
Difference between a conscious action and a reflex?
Conscious actions go through the brain and spinal chord, reflexes go to either the spinal chord or unconscious areas of brain
Job for?
Sensory neurone?
Relay neurone?
Motor neurone?
Sensory- transfers electrical impulses from receptor to CNS
Relay- transfers electrical impulses in CNS
Motor- transfers electrical impulses from CNS to effector
4 key features of a neurone and 2 of their adaptation
Nerve endings
Nucleus
Axon- long, thin to carry electrical impulses
Myelin sheath- insulating layer which speeds up conduction of electrical impulses
Synapse
A gap where two neurones meet
How do synapses work?
The nerve signal is transferred across the synapse by chemical messengers (neurotransmitters) which diffuse across the gap. Chemicals reach receptors, trigger electrical impulse in next neurone
Reflex
An involuntary action without conscious thought
2 benefits of reflexes
Helps to avoid danger/harm
Automatic, very fast
Reflex arc in detail
Stimulus detected by receptor, impulses from receptor to sensory neurone to CNS. Chemical crosses the synapse between sensory and relay neurone, then between relay and motor. Carries impulse to effector which is a muscle or gland.
Factors that influence reaction time
Age, gender, fatigue, distraction, alcohol
Reaction times required practical
Person A places arm on table with hand over edge, gap between thumb and finger. Person B holds ruler with 0cm at person A’s thumb, then drops it without telling them. Record the distance in line with Person A’s thumb, repeat this 10 times, calculate a mean. Then swap people.
2 bodily functions that reflex actions control
Breathing and digestion
Structure of brain
Made up of billions of neurones with different sections for different functions
3 key sections of the brain and what they are responsible for
Cerebral cortex- split into 4 lobes, responsible for consciousness, intelligence, memory and language
Cerebellum- responsible for coordinating muscular activity, balance
Medulla- responsible for unconscious activities
Hypothalamus job?
Pituitary job?
Regulate body temperature
Produce many different chemicals
3 key ways to study the brain
Studying people with brain damage
MRI scans
Electrical stimulation of the brain
2 problems with brain studies
Risky, easy to damage or potential side effects
Ethical concerns, is the patient capable of giving consent
Brain surgery
Benefits and risks
-Can remove tumours
Could cause brain damage
Could cause infections or stroke
Brain implant
Benefits and risks
-Hope for early stage Parkinson’s disease
Could cause brain damage
Radiotherapy or chemotherapy
Benefits and risks
-Can remove tumours
Can damage normal cells
Monoclonal antibodies
Benefits and risks
-Helps destroy cancer cells
Can cause red, sore and itchy skin
Stem cell therapies
Benefits and risks
-Helps repair damaged nervous system
Stem cells could be rejected
Sclera
Function?
Location?
Tough to protect and hold the eye in place
Outer layer
Cornea
Function?
Location?
Refracts light as it enters the eye
Transparent region of sclera at front of eye
Iris
Function?
Location?
Sets of muscles that control size of pupil, regulate light reaching retina
Side of pupil
Lens
Function?
Location?
Clear disc, fine-tunes the light rays
Held in place by ciliary muscles and suspensory ligaments
Retina
Function?
Location?
Made up of light sensitive receptor cells, contains cone and rod cells
Back of the eye
Optic nerve
Function?
Location?
Carry impulses from the retina to the brain
Back of the eye, leading to the brain
What happens in the iris when in bright light?
Result?
Circular muscles contract, radial muscles relax
Pupil constrict, less light, less damage to light sensitive receptor cells
What happens in the iris when in dim light?
Result?
Circular muscles relax, radial muscles contract
Pupils dilate, more light let in
How is light refracted?
Refracted at cornea, refracted at lens, focused directly on retina or vision is blurry.
Image is upside down but brain interprets it the right way up.
Accomodation
Process of changing the shape of the lens to focus on near or distant objects
Distant object
Rays?
Suspensory ligaments?
Ciliary muscles?
Lens?
Parallel
Tighten
Relax
Flat, thin
Near object
Rays?
Suspensory ligaments?
Ciliary muscles?
Lens?
Diverging
Loosen
Contract
Short, fat, thick
Hyperopia
Means?
Image formed?
Why?
Correct it with?
Long sighted, can see far away
Image formed behind retina
Lens too weak, eyeball too short
Convex lens
Myopia
Means?
Image formed?
Why?
Correct it with?
Short sighted, can see close by
Short of retina
Lens too strong, eyeball too long
Concave lens
Convex lens shape?
Concave lens shape?
Convex- oval
Concave- sand timer
3 new ways to overcome myopia and hyperopia
Contact lenses
Laser eye surgery
Replacement lens
Contact lenses
Ads & dis
Ads- Can’t be seen, easier to play sports, can last a long time or be thrown away
Dis- Need to be sterile to prevent eye infections
Laser eye surgery
Ads & dis
Ads- Can reduce thickness or change shape of cornea
Dis- Only available to adults, requires surgery
Replacement lens surgery
What is it?
Ads & dis
A permanent lens on top of or replacing previous lens
Ads- Permanent
Dis- Can damage retina, cause infections
