The senses and information processing

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Lesson notes

Purpose of the Nervous System

The nervous system is a complex network that transmits nerve impulses between different parts of the body.
Nerves receive stimuli from inside the body or the environment (e.g., ears, eyes, skin, tongue).
Stimuli are turned into impulses sent to the brain and spinal cord.
Stimulus is singular; stimuli is plural.

Components of the Nervous System

Nerves are long fibres that transmit messages between the brain/spinal cord and the rest of the body.
Each nerve is a bundle of nerve cells called neurons.
The brain is inside the skull and is part of the central nervous system; different areas have different functions and communicate.
The spinal cord runs from the brain through the spine, protected by the vertebral column, and is also part of the central nervous system.
The peripheral nervous system connects the central nervous system to muscles and organs.
Sensory organs (ears, nose, eyes, skin, tongue) collect information and send it via sensory nerves to the central nervous system.

The nervous system: brain, spinal cord and nerves

Main Processes: Sending and Receiving Impulses

Nerve cells in the brain send and receive multiple messages as electrical impulses.
The central nervous system interprets signals, enabling us to sense the world.
Nerve impulses travel at up to 274 km per hour.
The brain uses about 20% of the body's energy despite being less than 2% of body weight.

Sensory Processes: Hearing and Seeing

Hearing: Sound waves are transformed into electrical signals in the ear, traveling along the auditory nerve to the brain.
Seeing: Light enters the eye, stimulates specialized cells, and signals travel via the optic nerve to the brain for interpretation.

Sensory Processes: Feeling, Tasting, Smelling

Feeling: Skin has millions of receptors that respond to pressure, pain, temperature, and movement.
Tasting: Taste buds on tongue and mouth distinguish sweet, sour, bitter, salty; work closely with nose receptors.
Smelling: Nerve cells in the nose respond to air molecules; brain recognizes about 10,000 different smells.

Regulating Body Functions

The nervous system maintains balance (homeostasis) in the body.
It regulates body temperature to keep it around 37°C.
If too hot, the brain triggers sweating to cool down; if too cold, shivering generates heat.

Health Issues: Trauma and Stroke

Damage to the brain or spinal cord can be devastating; e.g., neck injuries can cause paralysis.
A stroke occurs when blood flow to the brain is stopped, causing brain cells to die within minutes.
Stroke can lead to loss of brain function.

How a stroke happens

Health Issues: Degenerative Disorders

Degenerative disorders cause gradual loss of function over time.
Examples include Alzheimer's Disease, Parkinson's Disease, and Multiple Sclerosis.

Slides

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Practice questions

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1.What is the plural form of the word 'stimulus'?
Easy
- Astimuli
- Bstimuluses
- Cstimulum
- Dstimula
2.Which of the following is NOT a sensory organ?
Easy
- Aears
- Bnose
- Ceyes
- Dskin
- Etongue
- Fheart
3.What is the main function of the nervous system?
Easy
- ATo transmit nerve impulses between different parts of the body
- BTo pump blood around the body
- CTo digest food
- DTo produce hormones
4.Which part of the nervous system is made up of the brain and spinal cord?
Easy
- ACentral nervous system
- BPeripheral nervous system
- CSensory organs
- DNerve tissue
5.Which nerve carries signals from the eye to the brain?
Easy
- AOptic nerve
- BAuditory nerve
- COlfactory nerve
- DSpinal nerve
6.What is the role of receptors in the skin?
Easy
- ATo respond to pressure, pain, temperature, and movement
- BTo produce sweat
- CTo detect light
- DTo transmit sound waves
7.Which of the following is a degenerative disorder of the nervous system?
Medium
- AStroke
- BAlzheimer's Disease
- CBladder infection
- DBroken neck
8.What happens when blood flow to the brain is stopped?
Medium
- ABrain cells begin to die, possibly leading to a stroke
- BThe brain grows larger
- CThe body temperature increases
- DThe person becomes more sensitive to light

Revision notes

## The Senses and Information Processing ### How We Sense the World - **Sensory receptors** detect stimuli (light, sound, chemicals, pressure, temperature) and convert them into electrical signals (action potentials). - These signals travel along **afferent neurons** to specific brain regions for processing and interpretation, creating our perception. - The brain also stores memories and controls behavior and immediate responses. ### Types of Sensory Receptors 1. **Chemoreceptors** – detect chemicals (taste, smell, oxygen levels). - *Distance chemoreceptors*: in nose for smells. - *Direct chemoreceptors*: taste buds on tongue; aortic bodies sense oxygen. 2. **Photoreceptors** – detect light (vision). - **Rods**: very sensitive to light intensity; allow dim-light vision. Humans have ~20:1 rods to cones. - **Cones**: respond to color; three types for blue, green, red. - **Ganglion cells**: some are photosensitive (1–2% in retina). 3. **Mechanoreceptors** – respond to mechanical forces (pressure, stretch, vibration). - *Slowly adapting type 1*: small receptive fields, sense form and roughness. - *Slowly adapting type 2*: large receptive fields, sense stretch. - *Rapidly adapting*: small receptive fields, sense slip. 4. **Thermoreceptors** – detect temperature changes. ### Receptive Fields - The **receptive field** is the area (body or environment) that a receptor or receptor cell responds to. - Example: the part of the world an eye can see is its receptive field; the light each rod or cone detects is its receptive field. ### Key Concepts - **Transduction**: converting a stimulus (e.g., light, chemical) into an electrical action potential. - **Sensory systems**: vision, hearing, touch, taste, smell, balance, and visceral sensation. - **Action potential**: the electrical signal that travels along neurons to the brain.

Sensory receptor: A specialized cell that detects a specific stimulus (light, chemical, pressure, etc.) and converts it into an electrical signal.
Receptive field: The area of the body or environment to which a receptor organ or receptor cell responds.
Transduction: The process by which a sensory receptor converts a physical stimulus into an electrical action potential.
Chemoreceptor: A receptor that detects chemical stimuli; includes olfactory and taste receptors.
Photoreceptor: A light-sensitive cell (rod or cone) that converts light into electrical signals for vision.
Mechanoreceptor: A receptor that responds to mechanical forces such as pressure, stretch, or vibration.
Thermoreceptor: A receptor that detects changes in temperature.
Action potential: An electrical signal that travels along a neuron, carrying information from a sensory receptor to the brain.

Flashcards

What is the main function of sensory receptors?

Sensory receptors detect stimuli from the environment and send signals to the brain for processing.

What are the four main categories of sensory receptors?

Chemoreceptors, photoreceptors, mechanoreceptors, and thermoreceptors.

What type of stimulus do chemoreceptors detect?

Chemical stimuli, such as odors (distance chemoreceptors) or tastes (direct chemoreceptors).

What type of stimulus do photoreceptors detect?

Light (electromagnetic radiation).

What type of stimulus do mechanoreceptors detect?

Mechanical forces like pressure, touch, stretch, or vibration.

What type of stimulus do thermoreceptors detect?

Temperature changes.

Name the five traditional human senses according to Aristotle.

Touch, taste, smell, vision, and hearing.

What is a receptive field?

The area of the body or environment to which a receptor organ and its receptor cells respond.

Give an example of a receptive field for the visual system.

The part of the world an eye can see is its receptive field.

What is the role of the brain in sensory processing?

The brain processes sensory information, stores memories, and coordinates responses.

What are the two types of chemoreceptors?

Distance chemoreceptors (detect gases, e.g., smell) and direct chemoreceptors (detect liquids, e.g., taste).

What are the three types of photoreceptors in the human eye?

Cones (color vision), rods (dim light vision), and photosensitive ganglion cells (involved in conscious vision).

Which photoreceptor type is most sensitive to light intensity?

Rods are very sensitive to light intensity and allow vision in dim lighting.

How do cones differ from rods in terms of color response?

Cones respond to specific wavelengths (blue, green, red/yellow), enabling color vision, while rods do not detect color.

What is the ratio of rods to cones in humans?

Approximately 20:1 (rods outnumber cones).

What are the four categories of cutaneous mechanoreceptors?

Slowly adapting type 1, slowly adapting type 2, rapidly adapting, and (not listed fully) others for slip perception.

What is the function of slowly adapting type 1 mechanoreceptors?

They have small receptive fields and respond to static stimulation, sensing form and roughness.

What is the function of slowly adapting type 2 mechanoreceptors?

They have large receptive fields and respond to stretch, producing sustained responses.

What is the function of rapidly adapting mechanoreceptors?

They have small receptive fields and underlie the perception of slip.

What is a sense organ?

A structure that converts physical stimuli from the environment into signals the brain can interpret.

What is the path of sensory information from receptor to perception?

Receptors transduce stimuli into action potentials, which travel along afferent neurons to specific brain regions for processing and interpretation.

What are some additional senses beyond the traditional five?

Pain, balance, kinesthesia (body movement), and temperature.

What is the role of the outer segment of a photoreceptor?

It captures light and transduces it into an electrical signal.

What neurotransmitter do photoreceptors release at their synaptic terminal?

Glutamate.

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