B3 Flashcards
How do nerve impulses travel through your nervous system (conscious)
Stimulus → Receptor cells → sensory neurone → Spinal cord → Brain → Spinal cord → motor neurone → Effector response
What do relay neurones do
Carry electrical impulses from sensory neurons to your motor neurons
And from the spinal cord to motor neurones
What is the reflex arc
The pathway of an impulse during a reflex reaction
Stimulus → receptor cells → Sensory neurone → spinal cord → motor neurone → effector →response
What does a motor neurone do
Carry electrical impulses from the cns to the effectors
What do sensory neurones do
Carry electrical impulses from receptor cells to cns
How are nerve impulses moved across neurones
The synaptic cleff is the area between two neurons.
A nerve impulse pushes the Neurotransmitters in vesicles to the edge of the presynaptic neurone
It diffuses across the postsynaptic neurone where it binds to the receptors (lock and key hypothesis) which creates a new nerve impulse
An example of a neurotransmitter used is adenosine
What are the main parts of an eye and what are there functions
Suspensory ligament - alters the shape of the lense (so does ciliary muscle)
Retina - contains photoreceptors (rods and cones)
Optic nerve - carries impulses to the brain
Lense - refracts and focuses light onto the retina (so does the cornea)
Pupil - allows light into the eye
Iris - controls the size of the pupil
What two muscles is the iris made of, and what are their purposes
The circular (inside) and radial (outside) muscles
When the circular muscle contracts the radial relaxes, letting less light into the eye
(Constriction)
When the radial contracts the circular relaxes, letting more light into the eye
(Dilation)
How do we focus on close objects.
The lens must be thicker to refract the light more.
The ciliary muscle contracts causing the suspensory ligament to slacken (reducing tension)
This makes the lens bulge and be more convex
How do we focus on far images
The lens needs to refract light less
The ciliary muscle relaxes, making the suspensory ligament taught, increasing tension.
The greater tension makes the lens stretch becoming less convex
What is the process of focusing on different distanced objects called
Accomodation
What is hyperopia and why does it occur.
Long sightedness (cant focus on close objects)
It occurs when the focal point is too far behind the eye or the eyeball is too short (or lens is less convex)
A convex (converging) lens is used to fix it (light refracts more)
What is myopia and why does it occur
Short - sightedness (cant focus far objects)
Focal point is in front of the retinas
Eyeball is too long / lens refracts too much
This is fixed using a concave lens which refracts the light outwards
What are rods and cones
Rods - respond to light
Cones - respond to colours
What is colour blindness
The inability to see certain colours due to a lack of cones
It is sex linked and more common in men
What are the parts of the brain?
Cerebrum - controls complex behaviour ( learning / voluntary movement / conscious thought(
Cerebellum - controls posture balance and involuntary movement
Hypothalamus - thermal / water (osmoregulation) regulation
Pituitary gland - controls hormones / stores and releases hormones
Medulla - controls automatic reactions like heart rate
What are hormones?
Chemical messengers that cause a response in specific target hormones
What is the endocrine system
All the endocrine glands and the hormones they produce.
An endocrine gland is a gland which secretes hormones
What is a target organ
Organ a hormone has effect on
How are hormones carried
In the blood stream in plasma
How are the endocrine system and the nervous system related
They both send messages around the body for a response.
Together they control and coordinate body processes
They provide information about changes in your environment
What are target cells and what do hormones do to them
Target cells are cells which a hormone is able to bind to.
Hormones diffuse out of the blood and bind to receptors (with a complimentary active site) found on the cells membrane or cytoplasm
Differences between the nervous system and endocrine system
Nerves - travel fast through electrical impulses, and act for a short time over a small area
Hormones - travel slower through the blood, and act for a longer time for a larger ara
Name 3 hormones, what they do, and the gland they are released from.
Testosterone - Released from the testes, promotes growth of secondary male characteristics
Thyroxine - Released from the thyroid (found in your throat) gland and controls metabolic rate
Adrenaline - released from your adrenal gland (above the kidneys) and is responsible for your fight or flight response
What is negative feedback
A process in homeostasis:
A change away from the normal value is detected and your body works to return that value to normal through the use of effectors
What is homeostasis
A process which:
Maintains internal body conditions within a narrow range
What does adrenaline do
When you feel threatened or scared the brain (specifically your hypothalamus) signals the adrenal glands to secrete adrenaline
This results in:
Higher respiration rate, more oxygen is needed to produce more ATP
Increasing heart rate (to transport the oxygen elsewhere)
Blood diversion from non essential organs like skin or your digestive system to the blood.
What is TRH and what releases it
TRH - thyroid releasing hormone (released by the hypothalamus)
It travels through the blood stream and binds to the pituitary gland
What is TSH and what gland is it secreted by
TSH - thyroid stimulating hormone (released by the anterior pituitary gland)
Binds to the thyroid causing thyroxine to be produced
How is negative feedback used to keep thyroxine levels stable.
-The hypothalamus detects a change in thyroxine levels
-It releases TRH which is transported through the blood to the anterior pituitary gland
-once it binds to that TSH is released which then travels through the blood to the thyroid gland
-TSh binds to specific shaped receptors on the thyroid gland
-thyroxine is then produced
-the hypothalamus detects this and stops producing TRH
-the thyroxine increase inhibits the production of TSH
What is Goitre
A condition which causes a swollen thyroid gland due to an iodine deficiency
Iodine is required for the production of thyroxine, so people with goitre will have a lower metabolism
What is FSH
Follicle stimulating hormone - is secreted by the pituitary gland and travels to the ovaries where it causes an egg to mature
It also stimulates the ovaries to produce Oestrogen
What is LH
Luteinising Hormone - triggers ovulation (also comes from the pituitary gland)
Causes empty egg follicles to develop into the corpus luteum - so progesterone is released
Inhibits FSH and oestrogen
What is Oestrogen
Oestrogen is a hormone secreted by the ovaries and causes the uterus lining to build up
It inhibits FSH from being produced. And it stimulates the pituitary gland to release LH
What is progesterone
Progesterone is a hormone secreted by the corpus luteum in the ovaries. It maintains the uterus lining
This hormone remains high during pregnancy.
It inhibits FSH and LH
What is the menstraul cycle
The 28 day cycle where a woman’s body is prepared for pregnancy
What is the menstrual cycle
The 28 day cycle where a woman’s body is prepared for pregnancy
What happens during day 0-5 of the menstrual cycle
Menstruation (a period) will occur.
The uterus lining breaks down
What happens during day 5-13 of the menstrual cycle
The uterus lining thickens (high amounts of oestrogen)
What happens during day 14 of the menstrual cycle
Ovulation - an egg is released by the ovaries, and empty egg follicles break down into the corpus luteum
(High amounts of LH around / before day 14)
What happens during day 14-28 of the menstrual cycle
The uterus lining stays the same
(High amounts of progesterone)
What happens if an egg isnt fertilised by day 28
The uterus lining (endometrium) breaks down