Unit 2_Intro to Sensory Systems Flashcards
Where does perception begin?
At the receptor level
What triggers an electrical signal in a sensory receptor?
A stimulus
Once a stimulus triggers an electrical signal in a sensory receptor, information is then relayed/processed from cell to cell with the ultimate goal of reaching the cortex for what?
conscious perceptions
It is important to note sensations are needed to trigger responses like what?
reflexes, movements, and alertness
Almost all sensory information is sent to the cerebral cortex for perception via what?
The thalamus (Smell is the exception)
This large ovoid mass is the largest of the four components and each half of the brain contains one. In many individuals there is a short inter-thalamic adhesion that connects the two thalami across the third ventricle that lies between them. Contains nuclei that may be divided into 5 functional nuclear groups.
Thalamus
What comprises the nuclei of Group 1 - Sensory Group?
- lateral geniculate (LG) – Eye
- medial geniculate (MG) – Ears
- ventral posterolateral (VPL) – Body
- ventral posteromedial (VPM) - Face
These nuclei have connections with the basal ganglia and the cerebellum and are involved in motor control?
GROUP 2 – Motor Group
These nuclei have important connections with limbic system structures and are involved in emotions such as anxiety and also in memory?
GROUP 3 – Limbic Group
These nuclei are likely involved in the complex processing of sensory information?
GROUP 4 – Multimodal Group
Recent evidence suggests that these nuclei are involved in the regulation of consciousness along with roles in movement control and pain?
GROUP 5 – Intralaminar Group
What kind of neurons are sensory nerves?
Pseudounipolar
Sensation is transmitted via what type of nerves?
Peripheral nerves
The morphological distinction between _______ and _______ is blurred.
Axons
Dendrites
Where are cell bodies residing in the peripheral nervous system for sensory neurons?
Ganglions in the spinal cord
Having myelin on the peripheral nerve will do what?
Decrease capacitance and allow EPSP or IPSP to have same magnitude when it reaches cell body
What is a specialized cell or group of cells that transform a type of physical energy into an electrical signal?
Somatosensory Receptors
What are two structure types of Somatosensory Receptors?
Free nerve ending
Special receptor cell
A sensory neuron in a sensory ganglion whose peripheral process is specialized for reception?
Free nerve ending
A sensory neuron in a sensory ganglion whose peripheral process is connected to what?
Special receptor cell
Axons (fibers) with the largest diameter and most myelin have the greatest what?
conduction velocities
Axons (fibers) with the smallest diameter and little or no myelin have the slowest what?
conduction velocities
Axonal conduction velocity is inversely related to what?
Axonal resistance (Ra) and Axonal Capacitance (Cm)
Small diameter axons have what?
high resistance
Unmyelinated axons have what?
high capacitance
Large diameter axons have what?
low resistance
Myelinated axons have what?
low capacitance
Peripheral nerves contain what?
Both myelinated and unmyelinated axons
Axons associated with skin are named differently than what?
Those associated with muscle
The amount of stimulus relate to what?
Types of fibers being triggered
How are receptors classified?
based on the form of energy or chemical to which they respond
What receptors respond to mechanical deformation, detect vibration, tapping, pressure, stretch, etc., connected to
Group I (a and b)
Group II (A beta), and
Group III (A delta) nerve fibers?
Mechanoreceptors
What receptors respond to the presence of certain molecules, detect chemical changes such as glucose, oxygen and carbon dioxide changes in blood, connected to Group IV (C) nerve fibers?
Chemoreceptors
What receptors respond to non-painful temperature changes, warm receptors, cold receptors, connected to
Group III (A delta) and
Group IV (C) nerve fibers?
Thermoreceptors
What receptors are not necessarily responsive to one type of energy, but respond when the magnitude is sufficient to begin to cause tissue damage, connected to
Group III (A delta) and
Group IV (C) nerve fibers?
Nociceptors
What respond to light energy and are not connected to the Group 1-IV (A-C) nerve fibers but to specialized retinal ganglion axons?
Photoreceptors (rods and cones)
What convert physical and chemical energy into electrical signals through a process called transduction?
Receptors
What process is the following:
- local event (stimulus) at a receptor leads to a change in membrane conductance for specific ions (Na+, K+). The result is a net movement of + charge into the cell leading to a decrease in membrane potential or depolarization.
- depolarizes the receptor membrane and produces a RECEPTOR or GENERATOR POTENTIAL (these will be summed for action potentials).
Transduction
What are a local graded potential which are dependent on the stimulus intensity and may be subthreshold, threshold, or suprathreshold?
The amplitude of this potential is proportional to the stimulus intensity.
Receptor potentials
The potential will be transmitted around the receptor membrane until it reaches the beginning of what?
This area contains the voltage gated channels where, if the receptor potential is large enough and reaches threshold, it will generate an action potential which propagates down the peripheral nerve towards the CNS.
The distal end of axon or first node of Ranvier (if axon is myelinated).
CNS identification of a stimulus intensity is done by what?
frequency coding and population coding
What occurs with stimulus intensity; amplitude of receptor potential; frequency of action potentials to CNS all increase linearly?
Frequency (rate) coding
What occurs when stronger stimuli activate more receptors which activate more axons (fibers) which tells CNS that the intensity has increased?
Population coding
What occurs when each type of receptor usually only responds (easily; i.e. there is best stimulus) to one stimulus type?
Receptor specificity
What is the organization of central nervous system pathways that describes a relationship between a particular part of the body and a particular area of the brain (SENSORY MAP)?
Somatotopy
What are the basis of topography?
Receptive fields
What is the spatial domain (e.g., where on skin) of a sensory neuron in the sense organ where stimulation excites or inhibits the neuron?
The receptive field
What are small in areas such as the fingers and face, and huge in areas that don’t require much precision such as the back and thigh?
Receptive fields
What refers to the organization of central nervous system pathways that describes a relationship between a particular part of the body and a particular area of the brain (really CNS since spinal cord has this kind of organization)?
Somatotophy
What is a precise mapping of the projections at each station on each sensory pathway that enables our cortex to localize a sensory experience? It allows the CNS to encode for the localization and quality of the stimulus.
The sensory map - homunculus
What suggests that no matter how you stimulate a pathway you will have the same perception?
Labelled line theory
What occurs when receptor potential decreases in amplitude in response to constant maintained stimuli?
Adaptation
- slowly adapting receptors and rapidly adapting
- rapidly adapting receptors = better detection of changes in environmental stimuli
What is the lowest stimulus intensity that a subject can detect?
Absolute Sensory Threshold
Thresholds are NOT FIXED (can be raised or lowered)
What help shape more complex receptive fields within CNS?
Interneurons
