Biology Chapter: Irritability and Sensory Systems

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Questions and Answers

What does irritability enable organisms to do?

Grow and develop without stimuli

Reproduce without external influences

Respond to environmental changes for survival (correct)

Detect internal temperature changes only

Which of the following is NOT a characteristic of stimuli?

Stimuli can affect both animals and plants

Stimuli are always harmful to organisms (correct)

Stimuli can be internal or external

Stimuli may influence an organism's behavior

Which type of cells are responsible for detecting stimuli?

Receptors (correct)

Muscle cells

Nerve cells

Epithelial cells

How do sense organs relate to receptors?

They group certain receptors together for specific stimuli detection Signup and view all the answers

What is an example of an organism displaying irritability?

A plant growing towards sunlight Signup and view all the answers

What liquid flows out when the cornea is cut open?

Aqueous humour Signup and view all the answers

Which structure should be examined after cutting through the iris?

Ciliary body Signup and view all the answers

What should be avoided when picking up the lens?

Scratching the lens Signup and view all the answers

What structure is located underneath the retina?

Choroid Signup and view all the answers

What should be done with the ox eye and other materials after the practical?

Directed disposal Signup and view all the answers

What is the primary function of the brain as described?

Control centre of the body Signup and view all the answers

What type of coordination is associated with the nervous system?

Nervous coordination Signup and view all the answers

What is irritability in the context of organisms?

The capacity to detect stimuli and respond Signup and view all the answers

Which system is responsible for hormonal coordination?

Endocrine system Signup and view all the answers

Which organs are specifically dedicated to detecting light?

Eyes Signup and view all the answers

How does the brain contribute to vision?

Receives nerve impulses and interprets them Signup and view all the answers

What is the structure of the human eye described as?

Spherical organ Signup and view all the answers

What is a response in the context of stimuli and effectors?

The effect of an action by an effector Signup and view all the answers

What structure forms the outer layer of the eyeball?

Sclera and cornea Signup and view all the answers

Which layer of the eye is responsible for containing the iris and ciliary body?

Middle layer Signup and view all the answers

What is the role of the aqueous humour in the eye?

It fills the anterior chamber. Signup and view all the answers

What part of the eye is described as the white, opaque fibrous coat?

Sclera Signup and view all the answers

Which of the following is the inner layer of the eye?

Retina Signup and view all the answers

What fills the posterior chamber of the eye?

Vitreous humour Signup and view all the answers

The conjunctiva serves what function in the eye?

Covers the sclera Signup and view all the answers

Which component is not part of the internal structure of the eye?

Conjunctiva Signup and view all the answers

What happens to the ciliary muscles when focusing on a near object?

They contract Signup and view all the answers

What effect does focusing on a distant object have on the lens?

The lens becomes thinner Signup and view all the answers

What changes occur in the suspensory ligaments when looking at a near object?

They slacken Signup and view all the answers

Which condition corresponds to the eye focusing on a distant object?

Lens becoming thinner and slackening ligaments Signup and view all the answers

During accommodation, what is the primary change in the lens shape when focusing on near objects?

The lens becomes more convex Signup and view all the answers

When a person with normal vision focuses on a near object, what happens to the light refraction?

It increases Signup and view all the answers

Which visual condition allows a person to see near objects more clearly than distant ones?

Short sight Signup and view all the answers

What happens to the tension in the suspensory ligaments when focusing on a near object?

It decreases significantly Signup and view all the answers

What is the primary function of the auditory centre of the brain?

To produce the sensation of hearing Signup and view all the answers

Which part of the ear vibrates to transmit sound waves to the cochlea?

Eardrum Signup and view all the answers

What is a common cause of conductive hearing loss?

Problems in the outer or middle ear Signup and view all the answers

How does a hearing aid assist those with hearing loss?

By increasing the amplitude of sound waves Signup and view all the answers

What role do sensory hair cells play in hearing?

They receive and transmit nerve impulses Signup and view all the answers

Which component stimulates the auditory nerve in those with cochlear implants?

Electrical impulses Signup and view all the answers

What does the cochlear implant's sound processor do?

Captures sounds from the environment Signup and view all the answers

Which structure in the cochlea is affected by wave movements to generate nerve impulses?

Hair cells Signup and view all the answers

Study Notes

Stimuli, Receptors, and Responses

Organisms can detect and respond to stimuli (changes in their environment)
Irritability is the ability of an organism to detect stimuli and produce appropriate responses.
This allows organisms to escape from danger, find food, or attract mates.

Chapter Preview

80% of environmental information is processed through the eyes.
Human eyes detect light; human ears detect sound; and plants respond to light through phototropism.

Irritability

Organisms detect external or internal changes in their environment (stimuli).
They produce a response to these stimuli.

Receptors

Sensory cells that detect stimuli are called receptors.
Different types of receptors detect different stimuli.
Specialized groups of tissues called sense organs contain receptors.

Human Receptors

Receptor Type	Stimulus Detected	Sense Organ(s)
Photoreceptor	Light	Eye
Mechanoreceptor	Sound (pressure waves), Touch (pressure)	Ear, Skin
Chemoreceptor	Chemicals in air, Food	Nose, Tongue
Thermoreceptor	Changes in temperature	Skin

Coordination Between Receptors and Effectors

Receptors detect stimuli and convert them into nerve impulses.
Impulses travel along nerves to the control centre (usually the brain).
The brain interprets these impulses as sensations.
The brain can also send impulses to effectors (muscles or glands) which then produce a response.

Human Eyes as the Sense Organ for Detecting Light

Eyes are spherical organs situated within bony sockets (orbits) in the skull.
Eyebrows, eyelashes, and eyelids protect eyes from foreign objects and bright light.
Tears contain lysozyme, an enzyme that kills bacteria, keeping the eyes moist and clean.

Internal Structures of the Eye

Sclera (white of the eye) and cornea (transparent front of the eye) form the outer layer.
Choroid, ciliary body, and iris form the middle layer.
Retina forms the inner layer.
The retina consists mostly of photoreceptors.
Rod cells are in charge of black and white vision.
Cone cells are in charge of colour vision.
The yellow spot is where cone cells are concentrated.
The optic nerve transmits signals to the brain.

Anterior and Posterior Chambers

The aqueous humour fills the anterior chamber, between cornea and lens.
The vitreous humour fills the posterior chamber, between lens and retina.
These humours help maintain the shape of the eyeball.

Eye Defects and Their Correction

Short sightedness (myopia): Eyeball too long or lens too thick; distant objects appear blurry; corrected with concave lenses.
Long sightedness (hyperopia): Eyeball too short or lens too thin: near objects appear blurry; corrected with convex lenses.

Colour Blindness

Deficiency of one or more types of cone cells.
Difficulty distinguishing colours, especially red-green, is a common type.

Eye Accommodation

The eye's lens changes shape to focus on objects at different distances.
Focusing on near objects: Ciliary muscles contract, suspensory ligaments relax, lens becomes thicker.
Focusing on distant objects: Ciliary muscles relax, suspensory ligaments tighten, lens becomes thinner

Human Ears as the Sense Organ for Detecting Sound

Outer ear: Pinna collects sound waves; auditory canal transmits waves to eardrum.
Middle ear: Ear bones amplify vibrations and transmit them to oval window.
Inner ear: Fluid vibrations stimulate sensory hair cells; these send nerve impulses to the brain where sounds are interpreted.

Phototropic Responses in Plants

Phototropism is the directional growth of a shoot or root in response to light.
Shoots are positively phototropic (grow towards light).
Roots are negatively phototropic (grow away from light).
Auxins are plant hormones in charge of phototropism.
Auxin concentration is higher on the shaded side, triggering differential growth resulting in the plant bending towards the light.

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Description

This quiz explores the concepts of irritability and sensory systems in organisms. It covers topics such as the characteristics of stimuli, the role of sense organs, and the functions of the brain in response to stimuli. Test your knowledge on biological responses and structures related to sensory perception.