teacher 3: 1 sensory system

L Sensory

3 main Components of Sensory System

1) Sensory receptors (detect stimuli)

2) neural pathways (transmit info)

3) Brain regions ( process and inetrgate info)

5 receptors

receptors convert physical/chemical stimuli into electrical; signals based on modality

Photoreceptors

Sensory receptor in the eye that detect light and energy

Mechanoreceptors

Sensory receptors that detect mechanical deformation of the cell membrane

Sensory receptors that detect when the cell membrane is physically pushed, stretched, or bent.

Basically: they sense physical pressure or movement.

Theremoreceptors

Sensory receptors that detect changes in temperature (warm & cold)

Chemoreceptors

sensory receptors that detect specfic chemcials in internal or externa, environments

Nociceptors

Sensory receptors specialized in detecting noxious or painful stimuli

Sensory Transduction

the process by which a sensory stimulus is converted into an electrical signal (receptor potential). Stimulus opens or closes ion channels, changing ionic current flow across the receptor membrane

2 receptor arrangment

1) Specialized Nerve endings: the part of the nerve that detects something and sends the signal to the brain/ spinal cord

2) Separate Receptor Cells: a specialized cell detects the stimulus becomes depolarizing/hyperpolarized, and releases chemical messengers (neurotransmitters) across a synapse onto the primary afferent neuron (photoreceptors, taste buds)

Receptor Potentials Vs Action Potential

Receptor potential: since it’s graded it can be small or big action potential depending whether it’s a small or big stimuli; small local changr in membrane voltage that can make the membrane less negative (depolarize) or more negative (hyperpolarize and fades as it spreads

Action Potentials: all or non ; triggered at the axon trigger zone

Sensory adaption

Slowly Adapting Receptors(Tonic): Keeps firing action potentials as long as the stimulus continues, telling the brain the stimulus is still there and how strong it is.

Rapidly Adapting Receptors (Phasic): Fires action potentials when a stimulus starts, stops, or changes, but stops firing when the stimulus stays the same. It detects changes or movement, like vibration or clothing touching your skin.

Primary Sensory Coding

Coding converts stimulus energy into meaningful CNS signals:

• Modality(type): determined by the receptor type activated Tells the brain what kind of sensation it is, based on which receptor and sensory pathway are activated. ex)

• Intensity: Encoded by:

  • Action Potential Frequency: stronger stimulus—> larger receptor potential—> higher AP frequency

  • Recruitment (summation): A stronger stimulus activates more sensory receptors nearby, causing more sensory neurons to send signals to the brain.

  • Location: Determined by:

    • Receptive field site on the body or map representation in the brain

    • Acuity (precision): how accurately you can tell where a sensation is coming from.

Lateral Inhibition

• Primary afferent neurons at the center of a stimulus fire strongly and activate inhibitory interneurons, which suppress signals from nearby afferent neurons, making the center signal stand out.

  • Purpose: shaprens contrast, pinpoint stimulus location n

What’s is a pathway? & 5 diff Ascending pathways

Pathways: Multi-neuron chains (primary afferent —> secondary neuron)

1) Specific Ascending Pathways: Carry information about one specific modality (sensory) (like touch or temperature) to the specific primary sensory cortical area which processes it.

2) Nonspecific Ascending Pathways: Receive information from multiple types of sensations (like pain, temperature, and touch) and send general information about alertness/arousal through the reticular formation

3) Divergence: One primary afferent neuron branches out and connects with multiple interneurons, spreading the signal to different areas and helping produce a reflex response.

4) Convergence: multiple primary afferent neuron connects into one interneuron

5) Central Control: the brain can turn sensory signals up or down before they reach the brain.

Perception vs. Association Cortex

Primary: Receives direct sensory information from a specific sense and registers the basic/raw details of the stimulus.

Association Cortex: Combines information from the primary sensory cortex with memory, emotion, attention, motivation, and languageto create a conscious perception and understand what the stimulus means.