Biology π | Coordination and response | 14 Flashcards
What do electrical impulses travel along?
Electrical impulses travel along neurones
What are the two parts of a mammallian nervous system?
- Central nervous system (CNS)
- Peripheral nervous system (PNS)
What does the CNS consist of?
The brain and spinal cord
What does the PNS consist of?
The nerves outside of the brain and spinal cord
What is the role of the nervous system?
Coordination and the regulation of body functions (via electrical impulses).
Define Dendrites
Tree-like projections that connect to other neurons and recieve electrical impulses from them.
Define Axon
A long fibre on a neuron which electrical impulses travel down
Define Myelin Sheath
Fatty sheaths that insulate an axon
What is the function of sensory neurons?
To send information to the central nervous system
Which part of the nervous system is a sensory neuron found?
In the Peripheral nervous system
What are the identifying features of a sensory neuron?
- A receptor cell
- Myelin sheaths
- A cell body branching off at the middle of the axon
- They are long
What is the function of relay neurons?
To directly connect a sensory neuron to a motor neuron
In which part of the nervous system are relay neurons found?
In the Central Nervous System
What are the identifying features of a relay neuron?
- No myelin sheaths
- Small cell body at one end with many dendrites branching off of it
- Short
What is the function of motor neurons?
They carry impulses from the CNS to effectors (muscles + glands)
Where are motor neurons found?
In the Peripheral Nervous System
What are the identifying features of a motor neuron?
- They have mylein sheaths
- They are long
- They have a large cell body at one end with long dendrites branching off of it
- On one end, they are connected to an effector
What are the two parts of the PNS?
- Somatic Nervous System (SNS)
- Automatic Nervous System (ANS)
What is the Somantic Nervous Sytem for?
Voluntary control of the body movements via skeletal muscle effectors
What is the Automatic Nervous System for?
Involuntary actions via muscle and gland effectors
Why do Mylein sheaths exist?
They insulate nerve fibres so electrical impulses can be passed fast: simply jumping from uninsulated sections to other uninsulated sectons.
What is a voluntary action?
A conscious decision to carry out a particular action, with our brain involved
What is an involuntary action?
An unconcious desicion that does not involve the brain. Generally these are essential to basic survival.
Which type of action is quicker: voluntary or involuntary?
Involuntary actions are quicker
Define reflex arc?
A means of automatically and rapidly integrating and coordinating stimuli with the responses of effectors involuntarily.
Does the reflex arc involve the brain?
No.
Describe a reflex arc to a stimulus, in steps.
- Sensory receptor recieves stimulus
- The signal travels along a sensory neurone
- The synapse at the end of the sensory neurone carries a message to the relay neurone
- The signal travels along the relay neuron, transmitted to a motor neuron
- The signal travels along the motor neurone
- An effector recieves the signal and carries out a response.
What are examples of involuntary actions?
- Coughing
- Knee jerk reflex
- Pupil reflex
Define stimulus
Any change either internal or external which leads to a response
Define synapse.
A junction between two neurones
How is information transmitted from one neuron to the next?
Neurotransmitters are diffused across the synaptic gap
How are synapses unidirectional?
They can pass information in only one direction because only the presynaptic neuron has vesicles of neurotransmitters
What is the function of vesicles in neurons?
Vesicles contain neurotransmitters in the presynaptic neuron, holding them until they recieve an impulse to release them.
What is the synaptic gap / cleft?
The tiny gap between two neurons: impulses do not cross it, but the neutrotransmitter chemicals do
What is the function of receptor proteins in synapses?
They detect the neurotransmitters and stimulate electrical impulses in response
Describe the events at a synapse when transmitting a signal.
- An impulse stimulates the release of neurotransmitter molecules from vesicles into the synaptic gap
- The neurotransmitter molecules diffuse across the gap
- Neurotransmitter molecules bind with receptor proteins on the next neurone
- an impulse is then stimulated in the next neurone
What is the eye?
The sense organ responsible for sight
What is an antagonistic muscle?
A muscle that opposes the action of another
In a pair of antagonistic muscles, which muscle would be the agonist and which one would be the antagonist?
The agonist would contract while the antagonist relaxes
Define sense organ
Groups of receptor cells responding to
specific stimuli: light, sound, touch, temperature and chemicals.
Cornea function
Refracts light
Iris function
Controls how much light enters the pupil
Lens function
Focuses light onto the retina
Retina function
Has light receptors that are sensitive to light of diferent colors
Optic nerve function
Carries impulses to the brain
Why do we have a blind spot?
Where are optic nerve sends signals to the brain, our cones and rods are distrupted
What two muscles are involved in the pupil reflex?
The radial muscle and the circular muscle
The circular and radial muscles are __
Antagonistic
What are the actions of the radial and circular muscles in low light?
Radial muscles contract and become shorter to pull the pupil out, making it wider. The circular muscle relaxes.
What are the actions of the radial and circular muscles in bright light?
Circular muscles contract and become shorter to reduce the size of the pupil. The radial muscles relax.
Why do we have the pupil reflex?
- It allows us to see better in the dark by letting more light in
- It protects our eyes in the day from being overloaded with light
What is the process of accomodation for?
For our eyes to adjust for near and distant objects
What is the muscle involved in accomodation?
The ciliary muscle
How do ciliary muscles help with accomodation?
Their contractions and relaxations are able to stretch the lens to different lengths that cause different amounts of refractions.
When an object is nearby, what are the actions of ciliary muscles?
The ciliary muscles contract so that the lens gets rounder and thicker
What are the suspensory ligaments?
They are ligaments that hold the lens in conjunction with the ciliary muscles
When an object is nearby, what processes happen in accomodation?
- The ciiary muscles contract
- Suspensory ligaments become relaxed
- Lens becomes rounder and thicker
When an object is far away, what processes happen in accomodation?
- The ciliary muscles relax
- Suspensory ligaments become stretched
- Lens becomes flatter and thinner
When an object is near to the eye, how does refraction change?
The amount of refraction increases
When an object is far from the eye, how does refraction change?
The amount of refraction decreases
What are the two types of receptors in the eye?
Rods and cones
Function of rods
Provide low detail, black & white images.
Function of cones
Provide detailed, coloured images
When are rods used?
In low-intensity light
When are cones used?
In high intensity light
Where in the eye are rods found?
Packed most tightly around edge of retina
Where in the eye are cones found?
Most tightly packed at fovea
What are the three types of cone cells?
Red, green, and blue. These colors are added together to create an array of visible color
What is the fovea?
The part of the retina where the cone cells are very tightly packed.
Where in the eye is light focused to?
To the fovea
Define hormone
A chemical substance, produced by a gland and carried by the blood, which alters the activity of one or more specific target organs
Where is adrenaline produced?
In the adrenal gland
Where is insulin produced?
In the pancreas
Where is testosterone produced?
In the testes
Where is oestrogen produced?
In the ovaries
What system are hormones and glands a part of?
The endocrine system
What is adrenaline?
The hormone secreted in βfight or flightβ situations
What are the effects of adrenaline?
- Increases heart rate
- Increases pupil diameter
- Increases breathing rate
Where is glucagon produced?
In the pancreas
How does speed of action compare between the nervous and hormonal system?
Speed of transmission is very rapin in the nervous system, but can be slow in the endocrine system
How does duration of effect compare between the nervous and hormonal system?
In the nervous system, the effect is usually within seconds, but in the hormonal system, it may take years, such as in puberty
Where is glucagon produced?
The pancreas
Define homeostasis
The maintenance of a
constant internal environment needed by a living organism
Via what concept does homeostasis work?
Negative feedback
How does negative feedback happen in our bodies?
Information about the body is sent to the brain by sensory receptors. The brain then coordinates a response to keep conditions within the normal range
What happens when blood glucose is too high?
- High blood glucose
- Insulin secreted
- Signals liver; stores excess glucose as glycogen
- Blood glucose concentration falls
- Normal blood glucose!
What happens when blood glucose is too low?
- Low blood glucose
- Glycogen secreted
- Signals liver to break down glycogen into glucose, releasing it
- Blood glucose concentration rises
- Normal blood glucose!
Which hormone is responsible for the storing of excess glucose?
Insulin
Which hormone is responsible for the release of glucose from glycogen?
Glucagon
What is type 1 diabetes caused by?
The death of insulin-secreting cells or lack of them.
What is the treatment for type 1 diabetes?
- Injecting insulin to lower blood glucose concentration
- Reducing carbohydrate intake
How do our body hairs change depending on temperature?
They lie flat when it is too hot, and are raised when the temperature is too high
Which muscles are responsible for moving our body hairs?
Hair erector muscles
How do hair erector muscles raise and lower hair?
They contract to raise hair, and relax so that hair lies flat
Why is it beneficial for our hairs to raise in cold?
The raised hairs trap heat
Define vasodilation
When arterioles, which supply blood to the skin-surface capillaries, dilate to allow more blood near to skin surface to increase heat loss
In what conditions does vasodilation occur?
When it is too hot
Define vasoconstriction
When arterioles, which supply blood to the skin-surface capillaries, constrict to allow less blood near to skin surface to increase heat loss
In what conditions does vasoconstriction occur?
When it is too cold
How does sweating help us lose heat when it is too hot?
Water evaporates from our skin, so our surfaces lose energy, and our temperature lowers
How does shivering help us when its cold?
Shivering is muscle activity. This is an increase in metabolism, thus more release of energy via respiration, thus production of heat
What is the role of temperature receptors in homeostasis?
They sense heat and send impulses to the hypothalamus to do things to stabilise body temperature
What role does the brain have in temperature homeostasis?
In the hypothalamus, in the thermoregulatory centre, the use of corrective mechanisms are controlled
Define gravitropism
A response in which
parts of a plant grow towards or away from gravity
Define phototropism
A response in which parts of a plant grow towards or away from the direction of the light source
Define auxins
The plant hormones or growth substances that control tropisms
Where are auxins produced?
At cells in the tips of a plant
Positive VS Negative phototropism
Positive: When part of a plant grows towards the light
Negative: When part of a plant grows away from the light
Positive VS Negative gravitropism
Positive: When part of a plant grows towards gravity
Negative: When part of a plant grows away from gravity
What tropisms do roots have?
- Negatively phototropic
- Positively gravitropic
What tropisms do shoots have?
- Positively phototropic
- Negatively gravitropic
How do auxins control shoot growth?
- Auxin is made in the shoot tip
- Auxin diffuses through the plant from the shoot tip
- Auxin is unequally distributed in response to light and gravity
- Auxin stimulates cell elongation
How do auxins create positive phototropism?
Auxins accumulate in the darker side of the plant, which is not hit by light. Thus, this side of the plant grows faster and the plant grows towards light
How do auxins create positive gravitropism?
- Auxins tend to settle at the bottom of the root
- This causes the tip of root cells to stop from growing, causing the cells at the top of the root to grow faster
- Thus, the growth of top root cells causes the root to be pushed deeper into soil
