Biology - Paper 2
Biological Responses
C10 – Human Nervous System
10.1 - Principles of Homeostasis:
Homeostasis is the regulation of conditions inside your body and cells to maintain a stable internal
environment. Body temperature, water content of body and blood glucose concentration are all
controlled.
Receptors – Cells that detect changes (stimuli) in environment.
Coordination Centres – Areas that receive and process information from receptors and send out
signals for response.
Effector – Muscle or glands that bring about responses to stimuli, these responses restore optimum
levels of conditions.
10.2 - Structure & Function of Nervous System:
Nervous system helps with avoiding danger, finding food and mate.
When sensory neurone detects stimuli, ENI sent to neurons. Neurones reach Central Nervous
System in brain and spinal cord where motor neurones make effectors carry out response.
Stimuli – Receptor – Coordinator – Effector
10.3 - Reflex Actions:
Reflex – Unconscious and automatic responses to a stimulus
Breathing and food digestion is a reflex.
Process is:
• Impulses from receptor pass along sensory neurone to CNS
• At synapse between sensory and relay neurone in CNS. Neuro transmitter is released which
causes impulse to be sent along relay neurone.
• Chemical released at synapse between motor and relay causes impulses to be sent along
motor neurone to effector.
• Effector is muscle which contracts or gland which releases chemicals.
Stimulus – Receptor – CNS – Effector – Response
,10.4 - The Brain:
Cerebral Cortex – Consciousness, intelligence, memory and language.
Cerebellum – Coordinating muscular activity and balance
Medulla – Unconscious activities such as controlling heartbeat, gut movement and breathing.
Studying patients with brain damage – Damaged area and effect on patient can tell you what
damaged part of brain does.
Electrically Stimulating Brain – By exposing different areas and see what the effect is by pushing tiny
electrodes into tissue and zapping it.
MRI Scans – Detailed picture of brain produced to find what part of brain is active when doing
certain tasks.
Brain is delicate and difficult to investigate.
10.5 - The Eye:
Sclera – Supporting wall of the eye
Cornea – Transparent outer layer found at front of eye. It refracts into the eye.
Iris – Contains muscles to control diameter of pupil and amount of light entering eye.
Lens – Focuses light onto retina which has receptor cells sensitive to light intensity and colour.
Ciliary Muscles & Suspensory Ligament – Controls shape of lens
Optic Nerve – Carries impulses from receptors on retina to the brain
Pupil – Light passes through this opening in iris
Retina – Light sensitive layer
Iris Reflex – Light receptors detect bright light so pupil gets smaller. Circular muscles in iris contract
and radial muscles relax. Reduces amount of light entering eye. In dim light radial muscles contract
and circular relax so pupils get wider.
, 10.6 - Common Eye Problems:
Myopia is short sightedness and hyperopia is long sightedness
Myopia – Light focused in front of retina and is corrected with a concave lens that bends light rays
out before it reaches the eye.
Hyperopia – Light focused behind the retina and is corrected with a convex lens which helps bend
light rays in.
Contact Lenses – Hard and soft lenses, soft are more comfortable but have a higher risk of infection.
Hard last longer but need to be sterilised each night.
Laser Surgery – Treats myopia and changes shape of cornea. This makes it refract light less. Laser
surgery for hyperopia is also possible.
Replacement Lenses – Risks are damage to retina, cataracts develop if old lens is still there, and
infections.
C11 – Hormonal Condition:
11.1 - Hormone Control:
FSH – Stimulates ovaries to make oestrogen
TSH – Thyroxine production
ENDOCRINE GLAND HORMONE ROLE
Pituitary Growth, and sperm/egg release
Thyroid Metabolic rate in body
Pancreas Glucose levels
Adrenal Adrenaline
Ovaries Menstrual cycle
Testes Sperm production
11.2 - Control Blood Glucose Levels:
Insulin allows glucose to move from blood to cells, reducing blood glucose levels.
Biological Responses
C10 – Human Nervous System
10.1 - Principles of Homeostasis:
Homeostasis is the regulation of conditions inside your body and cells to maintain a stable internal
environment. Body temperature, water content of body and blood glucose concentration are all
controlled.
Receptors – Cells that detect changes (stimuli) in environment.
Coordination Centres – Areas that receive and process information from receptors and send out
signals for response.
Effector – Muscle or glands that bring about responses to stimuli, these responses restore optimum
levels of conditions.
10.2 - Structure & Function of Nervous System:
Nervous system helps with avoiding danger, finding food and mate.
When sensory neurone detects stimuli, ENI sent to neurons. Neurones reach Central Nervous
System in brain and spinal cord where motor neurones make effectors carry out response.
Stimuli – Receptor – Coordinator – Effector
10.3 - Reflex Actions:
Reflex – Unconscious and automatic responses to a stimulus
Breathing and food digestion is a reflex.
Process is:
• Impulses from receptor pass along sensory neurone to CNS
• At synapse between sensory and relay neurone in CNS. Neuro transmitter is released which
causes impulse to be sent along relay neurone.
• Chemical released at synapse between motor and relay causes impulses to be sent along
motor neurone to effector.
• Effector is muscle which contracts or gland which releases chemicals.
Stimulus – Receptor – CNS – Effector – Response
,10.4 - The Brain:
Cerebral Cortex – Consciousness, intelligence, memory and language.
Cerebellum – Coordinating muscular activity and balance
Medulla – Unconscious activities such as controlling heartbeat, gut movement and breathing.
Studying patients with brain damage – Damaged area and effect on patient can tell you what
damaged part of brain does.
Electrically Stimulating Brain – By exposing different areas and see what the effect is by pushing tiny
electrodes into tissue and zapping it.
MRI Scans – Detailed picture of brain produced to find what part of brain is active when doing
certain tasks.
Brain is delicate and difficult to investigate.
10.5 - The Eye:
Sclera – Supporting wall of the eye
Cornea – Transparent outer layer found at front of eye. It refracts into the eye.
Iris – Contains muscles to control diameter of pupil and amount of light entering eye.
Lens – Focuses light onto retina which has receptor cells sensitive to light intensity and colour.
Ciliary Muscles & Suspensory Ligament – Controls shape of lens
Optic Nerve – Carries impulses from receptors on retina to the brain
Pupil – Light passes through this opening in iris
Retina – Light sensitive layer
Iris Reflex – Light receptors detect bright light so pupil gets smaller. Circular muscles in iris contract
and radial muscles relax. Reduces amount of light entering eye. In dim light radial muscles contract
and circular relax so pupils get wider.
, 10.6 - Common Eye Problems:
Myopia is short sightedness and hyperopia is long sightedness
Myopia – Light focused in front of retina and is corrected with a concave lens that bends light rays
out before it reaches the eye.
Hyperopia – Light focused behind the retina and is corrected with a convex lens which helps bend
light rays in.
Contact Lenses – Hard and soft lenses, soft are more comfortable but have a higher risk of infection.
Hard last longer but need to be sterilised each night.
Laser Surgery – Treats myopia and changes shape of cornea. This makes it refract light less. Laser
surgery for hyperopia is also possible.
Replacement Lenses – Risks are damage to retina, cataracts develop if old lens is still there, and
infections.
C11 – Hormonal Condition:
11.1 - Hormone Control:
FSH – Stimulates ovaries to make oestrogen
TSH – Thyroxine production
ENDOCRINE GLAND HORMONE ROLE
Pituitary Growth, and sperm/egg release
Thyroid Metabolic rate in body
Pancreas Glucose levels
Adrenal Adrenaline
Ovaries Menstrual cycle
Testes Sperm production
11.2 - Control Blood Glucose Levels:
Insulin allows glucose to move from blood to cells, reducing blood glucose levels.
