Survival and response Flashcards

Question

Nervous system in resting state?

Answer 1

Difference in charge between inside and outside of cell - generated by ion pumps and ion channels There is a voltage across the membrane - potential difference Called the resting potential When stimulus is detected the cell membrane is excited and becomes more permeable, allowing more ions to move in and out of the cell - altering the potential difference Change in potential difference due to a stimulus is the generator potential A bigger stimulus means there is a bigger movement of ions and a bigger change in potential difference - bigger generator potential created If the threshold is passed an action potential will be reached - electrical impulse along a neurone Strength of the stimulus is measured by the frequency of action potentials as they are all one size

Answer 2

Pacinian corpuscles mechanorecptors - detect mechanical stimuli - pressure and vibration Found in skin Contain the end of a sensory neurone - sensory nerve ending - wrapped in layers of connective tissue lamellae

Answer 3

When the pacinian corpuscles are stimulated the lamellae are deformed and press on the sensory nerve ending Stretches the sensory neurones cell membrane, deforming the stretch-mediated sodium ion channels They open and sodium ions diffuse into the cell - creating a generator potential If the generator potential reaches the threshold, it triggers an action potential

Answer 4

Photoreceptors in the eye Light enters the pupil Amount of light that enters is controlled by the muscles of the iris Light rays are focused by the lens onto the retina - lines the inside of the eye Retina contains photoreceptor cells - detect light The fovea is an area of the retina where there are lots of photoreceptors Nerve impulses from the photoreceptor cells are carried from the retina to the brain by the optic nerve, which is a bundle of neurones Where the optic nerve leaves the eye is called the blind spot - no photoreceptor cells here - not sensitive to light

Answer 5

Light enters the light, hits the photoreceptors and is absorbed by light-sensitive optical pigments Light bleaches the pigment, causing a chemical change and altering the membrane permeability to sodium ions A generator potential is created and if it reaches the threshold, a nerve impulse is sent along a bipolar neurone Bipolar neurones connect photoreceptors to the optic nerve, which takes impulses to the brain

Answer 6

Two types of photoreceptor - rods and cones Rods are mainly found in the peripheral parts of the retina, cones are packed together in the fovea Rods and cones contain different optical pigments - sensitive to different wavelengths Rods only give information in black and white (monochromic vision), but cones give information in colour (trichromatic vision). There are three types of cones, each containing a different optical pigment - red sensitive, green-sensitve and blue-sensitive Stimulated in different proportions to see different colours

Answer 7

SENSITIVITY Rods are very sensitive to light (fire action potentials in dim light) - because many rods join one neurone - many weak generator potentials reach the threshold Cones are less sensitive (only fire action potentials in bright light) - because one cone joins one neurone - takes more light to reach the threshold and reach an action potential VISUAL ACUITY (basically resolution) Rods give low visual acuity because many rods join the same neurone, light from two points close together can't be told apart Cones give high visual acuity - cones are close together and one cone joins one neurone - When light from two points hits two cones, two action potentials are produced

Answer 8

Cardiac muscle is myogenic SAN (sinoatrial node = pacemaker), in the wall of the right atrium sends out waves of electrical activity into the atrial walls Right and left atria contract Band of non-conducting collagen tissues prevents the waves of electrical activity from being passed directly from the atria to the ventricles Transfers to AVN (atrioventricular node) AVN slight delay - make sure the atria have emptied Electrical activity travels to bundle of His - group of muscle fibres Travels to Purkyne tissue Carries the waves of electrical activity into the muscular walls of the right and left ventricles, causing them to contract simultaneously Diastole

Answer 9

Controlled by part of the brain - medulla oblongata Alters in response to internal stimuli Pressure receptors - baroreceptors - aorta and carotid arteries - stimulated by high and low pressure Chemical receptors - chemoreceptors - aorta and carotid arteries in the medulla - monitor the oxygen level in the blood and also the CO2 and pH (indicators of O2 levels) Electrical impulses sent along sensory neurones to the medulla Sends impulses along sympathetic or parasympathetic neurones (autonomic nervous system)

Answer 10

``` Baroreceptors detect high blood pressure Impulses are sent to the medulla Impulses along parasympathetic neurones Secrete acetylcholine (neurotransmitter) Binds to receptors on the SAN Effects the cardiac muscles Heart rate slows to reduce blood pressure back to normal ```

Answer 11

``` Baroreceptors detect low blood pressure Impulses are sent to the medulla Impulses along sympathetic neurones Secrete noradrenaline (neurotransmitter) Binds to receptors on the SAN Effects the cardiac muscles Heart rate speeds up to increase blood pressure back to normal ```

Answer 12

``` Chemoreceptors detect chemical changes Impulses are sent to the medulla Impulses along parasympathetic neurones Secrete acetylcholine (neurotransmitter) Binds to receptors on the SAN Effects the cardiac muscles Heart rate decreases to return O2, CO2 and pH levels back to normal ```

Answer 13

``` Chemoreceptors detect chemical changes Impulses are sent to the medulla Impulses along sympathetic neurones Secrete noradrenaline (neurotransmitter) Binds to receptors on the SAN Effects the cardiac muscles Heart rate increases to return O2, CO2 and pH levels back to normal ```