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BPK 205 Introduction to Human Physiology MIDTERM 2 Simon Fraser University
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BPK 205 Introduction to Human Physiology MIDTERM 2 Simon Fraser University
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BPK 205 Introduction to Human Physiology MIDTERM 2 SimonFraser University
proprioception - awareness of body movement and position in space
special senses processed consciously - - vision
- hearing
- taste
- smell
- equilibrium
somatic senses processed consciously - - touch
- temperature
- pain
- itch
- proprioception
somatic stimuli processed subconsciously - - muscle length and tension
- proprioception
visceral stimuli processed subconsciously - - blood pressure
- distension of GI tract
- blood glucose concentration
- internal body temperature
- osmolarity of body fluids
,- lung inflation
- pH of CSF
- pH and oxygen content of blood
4 main types of sensory receptors - - chemoreceptors
- mechanoreceptors
- thermoreceptors
- photoreceptors
adequate stimulus - the form of energy to which the sensory receptor is most responsive
receptor potential - - stimulus causes a change in membrane potential of the receptor
- can be depolarization of hyperpolarization
threshold stimulus - the minimum stimulus needed to generate enough of a receptor potential to
produce an intracellular response
- response can be AP firing or neurotransmitter release
large receptive fields - - primary receptive fields overlap to form one large secondary receptive field
- convergence of primary neurons allow simultaneous subthreshold stimuli to sum at the secondary
sensory neuron and initiate an action potential
no two-point discrimination - two stimuli that fall within the same secondary receptive field perceived as
a single point because only one signal goes to the brain
two-point discrimination - - two stimuli activate separate pathways to the brain
- the two points are perceived as distinct stimuli
,small receptive fields - - found in more sensitive areas
- fewer neurons converge
- secondary receptive fields are much smaller
perception threshold - minimum stimulus intensity required for activation of higher neurons in the
sensory pathway and, thus, transmission of the signal to the brain for perception
how are stimulus properties distinguished - - stimulus modality
- location
- intensity
- duration
stimulus modality determined by - - sensory receptor that is activated
- area of the brain to which the sensory signal is sent
labeled line coding - brain always associates the signal from a particular group of receptors with a
specific modality
olfactory pathway - - from the nose project through the olfactory bulb to the olfactory cortex
- does not pass through thalamus
sensory pathways - - project to the thalamus
- thalamus modifies and relays information to cortical centers
the receptive field - - all sensory neurons within one receptive field will project sensory info to the same
location in the cerebellum
, - sensory input from two adjacent receptive fields will project info to adjacent regions in the cortex
- sensitivity of the region is inversely proportional to the size of the receptive field
location of auditory signals - - exception to the use of receptive field for localization
- ear neurons sensitive to different frequencies
- brain uses differences in timing to locate sound
lateral inhibition - enhances contrast between activated receptive fields and inactive neighbors, which
makes a stimulus easier to perceive
stimulus intensity - coded by number of receptors activated and frequency of action potentials called
frequency coding
- frequency of action potential is proportional to stimulus intensity
stimulus duration - - coded by duration of action potentials
- some receptors can adapt, or cease to respond
- duration of a series of action potentials is proportional to stimulus duration
coding for stimulus intensity and duration - - receptor potential strength and duration vary with the
stimulus
- receptor potential is integrated at the trigger zone
- frequency of action potential is proportional to stimulus intensity
- duration of a series of action potentials is proportion to stimulus duration
- neurotransmitter release varies with the pattern of action potentials arriving at the axon terminal
tonic receptors - slowly adapting receptors that respond for the duration of a stimulus
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