Topic 5- Homeostasis and response Flashcards
(49 cards)
Sexual reproduction:
Invloves the joining of male and female gamtes, each containing genetic information from the mother or father.
* Sperm and egg cells in animals
* Pollen and egg cells in flowering plants
Meiosis:
- The cell makes copies of it’s chromosmes, so it has double the amount of genetic information
- The cell divides into two, both the cells have half the amount of chromosmes
- The cells divide again, producing four cells, each with a quarter amount of chromosmes
- These cells are called gametes and they are all genetically different from each other. This is because the chromosomes are shuffled during the process, resulting in random chromosomes ending up in each of the four cells.
Homeostasis:
- An organism’s ability to regualte it’s internal conditions, even when external conditions change.
- What needs to be regualted?
1. Blood glucose concentration
2. Body temperature
3. Water levels - Homeostasis maintains optimal conditions for enyme action and cell functions.
Automatic control systems:
- May invlove nervous responses or chemical responses
- All control systems include:
- Recpetors (cells that dectect a stimulus)
- Coordination centres (such as the brain, spinal cord and pancreas) that recieve and process information from receptors
- Effectors, muscles or glands which bring about responses which restore optimum levels.
The human nervous system:
Enables humans to react to their surroundings and co-ordinate their behaviour.
1. Information from receptors passes along receptors (cells)
2. As electrical impulses to the central nervous system (CNS).
3. The CNS coordinates a response- which may be muscles contracting or glands secreting hormones.
What is the central nervous system (CNS)?
The brain and spinal cord.
What is the PNS?
All other nerves.
Reflex:
- In a reflex arc, the signal passes by much quicker
- They are automatic and rapid- do not involve the concious part of the brain.
Structures in a reflex arc:
Stimulus→receptor→coordinator→effector→response
This is quicker than normal responses as you do not have to think about the response.
Synapse:
A gap between two neurones that trigger chemicals to be released.
The brain- cerebral cortex:
Resonsible for higher level functions:
* Memory
* speech
* problem solving
The brain - cerebellum:
Responsible for motor skills:
* Movement
* Balance
* Coordination
The brain- medulla:
Responsible for unconcious actions:
* Heart and breathing rate
* Signals to adrenal glands to release adrelanine
Electrically stimulating different parts of the brain:
- Can be stimulated electically by pushing an electrode intto the tissue and giving it a small zap of electricity. By observing the stimulation, scientists get a better idea of what those parts of the brain do.
MRI scans:
- Allow doctors to see brain activity without surgery.
- Issues with the brain are impossible/ difficult to treat safely.
Accomodation:
The eye’s ability to focus on near or distant objects.
Accomodation- near objects:
- Ciliary muscles contract
- So they have a smaller diameter
- Suspensory ligaments slacken
- Lens becomes fatter
- Light is refracted more
- Light rays are focused onto retina
Accomodation- distant objects:
- Ciliary muscles relax
- So they have a bigger diameter
- Suspensory ligaments tighten
- Lens becomes thin
- Light is refracted by a smaller amount
- Light rays are focused onto retina
Retina cells:
Consist of only rod and cone cells, which respond to light.
* Rods only detect light intensity
* 3 different types of cones; that are sensitive to red, blue or green wavelengths of light which provide colour information.
* These signals travel to the brain via the optical nerve
HYPEROPIA (long sightedeness):
Long-sighted people are unable to focus on near objects.
* The eyeball is too short, so light focuses behind the retina.
* Use glasses with convex lenses so light rays focus on the retina.
MYOPIA (short-sightedness):
Short-sighted people are unable to focus on distant objects.
* Eyeball is too long, so light focuses infront of the retina.
* Use glasses with concave lenses so that light rays focus on the retina.
Body temperature:
- Controlled by the thermoregulatory centre in the brain.
- Thermoregulatory centre contains receptors sensetive to the temperaure of the blood.
- Nervous impulses are sent to effectors
Body temperature is too high:
- Blood vessels dilate
- Sweat is produced from the sweat glands
- Both these mechanisms transfer energy from skin to environment.
Blood temperature is too low:
- Blood vessels constrict
- Sweating stops
- Skeletal muscles contract (shiver)
- Hair stands on end to trap air- layer of insulation
