Survival and response

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  • Created by: Science
  • Created on: 19-04-21 18:36

Survival and response

Stimulus - change in internal/external environment of an orgnaism resulting in a response 

Response - action or change an organism makes in reaction to a stimulus 

Stimulus - receptor - coordinator - effector - response

Taxes - directional response to a stimulus 

Kinesis - non-directional response to a stimulus where an organism changes its speed and rate of direction change depending on environmental conditions

Phototropism

  • Indoleacetic acid diffuses to shaded side
  • Stimulates cell elongation and shoots grow to the light 

Gravitrophism 

  • Indoleacetic acid diffuses to lower side of root
  • inhibits cell elongation and root grows towards gravity
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Survival and response

Peripheral nervous system

  • sensory neurone - impulses carried form receptor to CNS
  • motor neurone - impulses carried from CNS to effector
  • voluntary nervous system - coordinated response
  • autonomic nervous system - not voluntary 

Reflex arc

  • involuntary action, not coordinated
  • fast
  • bypasses coordinator

Pacinian Corpuscle

  • Resting potential present
  • Pressure applied opening stretch mediated sodium ion channels 
  • Sodium ions diffuse into neurone which depolarises the membrane resulting in an action potential
  • Sodium-potassium pumps cause repolarisation
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Survival and response

Rod cells

  • detect low light intensity
  • cannot distinguish different wavelengths
  • at peripheral of eye
  • low visual acuity 
  • rhodopsin breaks down causing action potential

Retinal convergence - multiple rods connected to single neurone (bipolar cell)

Spacial summation - more than one rod cell causes action potential

Cone cells

  • different cone cells respond to different wavelenght colours
  • each has one neurone (bipolar cell) so high visual acuity 
  • respond to high light intensity
  • at fovea
  • iodopsin breaks down to form action potential

Threshold value - energy required to produce action potential

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Survival and response

Heart contraction

  • Wave of electrical excitation spreads from Sinoatrial node (SAN)
  • Atrial muscles contract
  • Non-conductive tissue prevents wave moving into ventricle
  • Wave of excitation enters atrioventricular node (AVN)
  • Waves moves along purkyne tissue in bundle of His
  • Ventricular contraction occurs

ECG traces

  • P wave - polarisation of atria from SAN and atrial contraction
  • QRS wave - ventricular depolarisation and contraction
  • T wave - repolarisation of ventricle 
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Survival and response

Chemoreceptors 

  • found in carotid artery wall
  • Detects lower pH
  • Increases frequency of nervous impulses to medulla oblongata 
  • Increases impulses sent by medulla oblongata by sympathetic nervous system
  • SAN increases impulses increasing heart rate

High blood pressure

  • Baroreceptors in carotid arteries and aorta detect high pressure
  • More impulses sent to medulla oblongata
  • Increases impulses sent to SAN via parasympathetic nerve, decreasing heart rate

Low blood pressure

  • Baroreceptors in carotid arteries and aorta detect low pressure
  • More impulses sent to medulla oblongata
  • Increases impulses sent to SAN via sympathetic nerve, increasing heart rate
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Survival and response

Sympathetic nervous system 

  • increases heart rate
  • emergency controller 
  • heightens awareness 
  • fight or flight

Parasympathetic nervous system

  • slows heart rate
  • controls normal resting conditions 
  • conserves energy

myogenic - contraction is intiated in the height

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