| What is Homeostasis? | HOMEOSTASIS
Maintains optimal conditions for enzyme action throughout the body, as well as all cell functions. In the human body:
- blood glucose concentration
- body temperature
- water levels |
| What does the Body Control System Consist of? | - receptor cells, detect stimuli (changes in environment)
- coordination centre (brain/spinal cord/ pancreas), which processes info from receptors around the body
- Effectors (muscle/glands), bring about responses(muscle contractions or hormone release), restore optimum levels |
| What are the functions of Nerve Cells, Receptors & Effectors? | 1) Nerve Cells - bundle of neurons, adapted to carry electrical impulses from place to place. 3 main neurons: sensory, motor & relay. Features: long fibre (axon), carry messages up and down body; tiny branches (dendrons) branch of as dendrites & receive incoming impulses from other neurons
2) Receptors - Detect stimuli and stimulate electrical impulses in response. Sense organs contain a group of receptors that respond to specific stimuli: skin - touch, temperature, pain; tongue - chemicals; nose - chemicals; eye - light; ear - sound & position of head
3) Effectors - (muscles/glands) produce specific response to a detected stimulus (e.g. muscle contracting to move an arm; a gland releasing hormone into blood) |
| What does the Eye Consist of? | 1) Cornea - Refracts light - bends it as it enters the eye
2) Iris - Controls how much light enters the pupil (Bright - radial muscle relaxed, circular muscle contracts, pupil contratcs, vice versa)
3) Lens- Further refracts light to focus it onto the retina
4) Retina - Contains the light receptors (rods (more sensitive) and cones)
5) Optic nerve - Carries impulses between the eye and the brain
6) Sclera - Tough white outer layer of the eye. It helps protect the eye from injury |
| What are the 3 other corrections for vision defects? | 1) Contact lens - work like spectacle lenses(refract light), float on cornea surface
2) Laser Surgery - reshapes cornea surgically. Common for Myopia
3) Replacement lens - artificial lens implant (placed in front of original lens), corrects eye defect |
| How does the Reflex Arc Work? | 1. Receptor in skin detects a stimulus
2. Sensory neurone sends electric impulse to relay neurone (in spinal cord)
3. Motor neurone sends electric impulse to an effector
4. Effector produces response (muscle contraction...) |
| PRACTICAL: Ruler Drop Test (7 Stages) | 1) Person A holds out their hand with a gap between their thumb and first finger.
2) Person B holds the ruler with the zero at the top of person A's thumb
3) Person B drops the ruler without telling Person A and they must catch it.
4) The number level with the top of person A's thumb is recorded in a suitable table. Repeat this ten times.
5) Swap places, and record another ten attempts.
6) You can use the conversion table to help convert your ruler measurements into reaction time or just record the catch distance in cm
7) Repeat practical, this time with background noise or caffeine and compare results |
| What does the Brain Consist of? | 1) The cerebrum (the outer layer is called the cerebral cortex), is split into two hemispheres and is highly folded. It controls intelligence, personality, conscious thought and high-level functions, such as language and verbal memory.
2) The cerebellum, which controls balance, co-ordination of movement and muscular activity.
3) The medulla, which controls unconscious activities such as heart rate and breathing rate,
4) The hypothalamus, which is the regulating centre for temperature and water balance within the body |
| How is the Brain Examined (3 Methods & Risks)? | 1) BRAIN DAMAGE: 1848, Phineas Gage, when laying railway tracks, an iron rod went through his skull. Survived but his personality changed losing his inhibitions socially and emotionally. This allowed scientists to examine the effect on injuries on his brain activity
2) ELECTRICAL STIMULATION: Scientists stimulate parts of the brain w/ a weak electrical current, patients describe what they experience. If motor area is stimulated, patient makes an involuntary movement. visual area stimulate - may see a flash of colour. Electroencephalograms can be created and studied, to observe the electrical activity in the brain
3) MRI BRAIN SCANS: use strong magnetic fields and radio waves to show details of brain structure and function. Patients perform various tasks, by looking at scan, scientist can see which parts of the brain are active
4) RISKS: Brain surgery may be needed to remove the tumour or excess fluid like blood. Due to complexity & delicacy of the brain, treating and investigating is very difficult. Surgery can cause more damage/side effects |
| Compare what happens when focusing on near and far objects? | FOCUS ON NEAR OBJECT:
1) Ciliary muscle - Contract
2) Suspensory ligaments - slacken
3) Muscle tension - low
4) Lens shape - thickens
5) Light refraction - strong
FOCUS ON DISTANT OBJECT:
1) Ciliary muscle - relax
2) Suspensory ligaments - stretched
3) Muscle tension - high
4) Lens shape - thin
5) Light refraction - slight |
| What is The Nervous System? | NERVOUS SYSTEM:
- The CNS (brain and spinal cord)
- peripheral nervous system (nerve cells that carry info to or from the CNS) |
| How is an impulse sent across a neurone? | Over a synapse:
SYNAPSE - small gap where 2 neurons meet
1. An electrical impulse travels along the first axon:
2. This triggers the nerve-ending of a neurone to release neurotransmitters (chemical messengers )
3. These chemicals diffuse across the synapse & bind with receptor molecules on the membrane of the second neurone
4. The receptor molecules on the second neurone bind to the specific neurotransmitters released from the first neurone. This stimulates the second neurone to transmit the electrical impulse |
| What are the causes of short sight & how can it be corrected? | SHORT SIGHT(Myopia): can't focus on distant object properly. Caused by:
- Eyeball being elongated, distance between lens and retina is too great
- Lens being too thick & curved, light is focused in front of retina
Corrected by: Concave lens )( shape |
| What are the causes of Long sight & how can it be corrected? | LONG SIGHT(Hyperopia): can't focus on near object properly. Caused by:
- Eyeball being too short, distance between lens and retina is too small
- loss of elasticity in the lens - it cannot become thick enough to focus (which is often age-related)
Corrected by: Convex lens () shape |
