Communication & Homeostasis Flashcards
What is the role of receptors?
receptors detect stimuli- they are specific and only detect one particular stimulus e.g. pressure, light or glucose concentration
What are the different types of receptors?
some receptors are cells e.g. photoreceptors: they connect to the nervous system. Some are proteins on cell surface membranes e.g. glucose receptors are proteins found in the cell membranes of some pancreatic cells
What are effectors?
they are cells that bring about a response to a stimulus to produce an effect. These include muscle cells and cells found in glands.
What happens during cell signalling?
nervous system- cells communicate by secreting neurotransmitters which sends signals to adjacent cells e.g. nerve cells
hormonal system- cells release hormones which act as signals to distant cells; receptors allow cells to recognise the chemicals in cell signalling
What are the three different neurones and what do they do?
Sensory neurones- transmit nerve impulses from receptors to the CNS
Motor neurones- transmit nerve impulses from the CNS to effectors
Relay neurones- transmit nerve impulses between sensory neurones and motor neurones
What is the structure of the neurones?
have a cell body with a nucleus. the cell body has dendrites and dendrons that carry nerve impulses towards the cell body (dendrites are smaller branches of a dendron) axons carry nerve impulses away from the cell body.
What is myelination?
an electrical insulator
allows the impulses to transmit faster as electrical impulses jump from one node of Ranvier to the next.
the cells also provide nutritional support
What is the structure of a sensory neuron?
have short dendrites and one long dendron to carry nerve impulses from receptor cells to the cell body, and one long axon that carries nerve impulses from the cell body to the CNS
What is the structure of a motor neuron?
have many short dendrites that carry nerve impulses from the CNS to the cell body, and one long axon that carries nerve impulses from the cell body to effector cells
What is the structure of a relay neuron?
have many short dendrites that carry nerve impulses from sensory neurones to the cell body, and one axon that carries nerve impulses from the cell body to motor neurones
What happens during nervous communication?
stimulus is detected
a nerve impulse is sent along a sensory neurone
when the nerve impulse reaches the end of a neurone, chemicals take the information across the synapse to the next neurone
the CNS processes the information & decides what to do about it
sends impulses along motor neurones to an effector
Why are sensory neurones described as transducers?
the nervous system only sends information in the form of electrical impulses
sensory receptors convert the energy of a stimulus (light, kinetic, chemical) into electrical energy
What is resting potential?
when nervous system receptors are in resting state (not being stimulated) . There’s a difference in charge between the inside and outside of a cell- the inside is negatively charged relative to the outside. This is achieved by an imbalance in concentrations of Na + and K + achieved by active transport. This means there’s a voltage/potential difference across the membrane and it is said to be polarised.
What happens during resting potential?
sodium-potassium pumps use active transport to move 3 sodium ions out of the neurone for every 2 potassium ions moved in. Potassium ion channels allow the facilitated diffusion of potassium ions out of the cell. Voltage gated potassium and sodium ion channels are closed. In total, more positive ions move out than in making the outside +vely charged compared to the inside
What happens during generator potential?
When a stimulus is detected, the cell membrane is excited and becomes more permeable.
allows ions to move in and out of the cell, altering the potential difference. Stimulus excites the membrane more causing a bigger movement of ions therefore, a bigger change in potential difference.
What happens during the action potential?
if a generator potential is big enough it may reach the threshold level and trigger an action potential. An action potential is how impulses travel along a neurone.
What is the pacinian corpuscle?
Its skin tissue (mechanoreceptor) that detects pressure and vibrations. When it’s stimulated e.g. by a tap on the arm, the lamellas is deformed and press on the sensory nerve ending. This causes deformation of stretch-mediated sodium channels in a sensory neurones cell membrane. The Sodium ion channels open and sodium ions diffuse into the cell creating a generator potential. If the generator potential reaches a threshold it triggers an action potential.
What is the hormonal system?
It sends information as chemical signals and is made up of endocrine glands and hormones