Download Responding to the environment

RESPONDING TO THE
ENVIRONMENT- HUMANS
 Nervous system (nerves)
 Endocrine system (hormones)
Human nervous system
Need for a nervous system:
 Reaction to stimuli (changes in the
environment- external and internal)
 Coordination of the various activities of the
body
Examples of responses
Voluntary actions
 Eating a cake
 Riding a bicycle
 Walking
Involuntary actions
- Your heart beat
- Breathing
- Removing hand from
hot object
 Playing the piano
- Choking
 Coming to school
- Salivating
- Blinking
Central nervous system
Brain + Spinal cord
Protected by:
 Meninges (3 membranes)
 Skeleton (bone)
 Cerebrospinal fluid
Homework: Draw a labelled diagram of the section of
the brain, and annotate with the functions.(only
cerebrum, cerebellum, corpus callosum, Medulla
oblongata and spinal cord pg 188 without the skull etc.
NERVOUS SYSTEM
PERIPHERAL NERVOUS SYSTEM
12 pairs cranial nerves
31 pairs spinal nerves
CENTRAL NERVOUS SYSTEM
(CNS)
Brain +
Spinal cord
MOTOR NERVES
Conduct impulses from the
CNS to the effectors
AUTONOMIC NERVOUS SYSTEM
Conducts impulses from the CNS to the involuntary
muscles (smooth muscles and heart muscles) and
certain glands
SYMPATHETIC DIVISION
Prepares the body for action, ‘fight or
flight’
SENSORY NERVES
Conduct impulses from the
receptors to the CNS
SOMATIC NERVOUS SYSTEM
Conducts impulses from the CNS to the
voluntary muscles
PARASYMPATHETIC DIVISION
Enables body to return to normal
Cranial+spinal
Sympathetic branch
1. Increases heart rate
Parasympathetic
branch
1. Decreases heart rate
2. Relaxes walls of
bladder
3. Dilates pupils
2. Contracts wall of
bladder
3. Constricts pupils
4. Constricts many
arteries
5. Increases blood
pressure
4. Dilates arteries
5. Decreases blood
pressure
Brain structure
Cerebrum
Corpus
Callosum
cerebellum
hypothalamus
Spinal cord
Pituitary gland
medulla
brain functions
state the functions of each of the following parts of sensory and motor
neurons: nucleus, cell body, cytoplasm, myelin sheath, axon and dendrites.
 Reflex action: quick, automatic response to a
stimulus.
 Reflex arc: The nerve pathway taken in a reflex
action
A reflex arc
Reflex arc
 Stimulus → receptor (converted to
impulse) → sensory nerve → Spinal cord
(via dorsal root) → synapse → interneuron
→ synapse → (via ventral root) motor
neuron → effector
The knee jerk reflex action
Sometimes
called a
relay or
Connector
neurone
Another reflex action
Significance of a reflex
action
 Protects the body from further damage by
reacting quickly (from spinal cord not brain)
Disorders of the CNS
Alzheimer’s disease Ex 3 pg 204 (only 10 marks)
Multiple sclerosis Ex 4 pg 206 (only 10 marks)
(focus is on causes and symptoms)
Significance of synapses
 It allows messages to be passed from one
neuron to the next.
 Allows impulses to travel in one direction
only.
 Allows nerves to join or split (1 → many or
many→1)
 Removes continual background stimuli.
Consequences of brain and
spinal injury
 Brain injury pg 208
 Spinal injury pg 210
 Also stem cells research has potential to
repair damage
Negative effects of drugs on
the central nervous system
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Slows down reaction time,
causes loss of self control + even coma
Loss of memory
May damage the brain
Receptors
 the body responds to a variety of different
stimuli, such as light, sound, touch,
temperature, pressure, pain and chemicals
(taste and smell).
 receptors, neurons and effectors function
together in responding to the environment.
Human eye
 Draw a section of the human eye, provide all
labels and functions. (pg 221)
Binocular vision
2
eyes
 Use of two eyes with overlapping fields of
vision.
 It allows interpretation in 3D
Structure and function
Allows the front of the
eye to keep its bulging
shape.
Yellow spot – has
rods and cones that
allows one to see
fine detail
Separates the cornea
from the lens.
Sends light vibrations
to the visual cortex in
the cerebrum
Focuses the image
on the retina.
Light passes through it
The optic nerve leaves
the eye, no light
sensitive nerves
available
Controls the size of the
pupil
Allows the lens to change
shape during focusing
Together with the lens
focuses the image on the
retina
Image formation
 Light reflected from objects passes through the
cornea, aqueous humour, pupil, lens and vitreous
humour and falls on the retina where an image is
formed.
 All the structures named above but pupil bring about
refraction such that the image is focused on the retina
Bending light (refractions)
Structure responsible for
refraction are the cornea
and lens.
Rods and cones pick up
the images accordingly
as per their specific
adaptations.
In this way light stimulus
is converted into a nerve
impulse on the retina.
These impulses are
converted to the optic
nerve to the cerebrum to
be interpreted.
Accommodation
 Refers to the ability of
the eye to change the
shape (convexity) of the
lens to ensure a clear
image is formed on the
retina whether the
image is near or distant.
Near vision (<6m away)
(summarised pg 225 textbook)
• the cilliary muscles contract
•the sclera is pulled forward
• the suspensory ligaments slacken
• the tension on the lens decreases
• the lens becomes more convex
• the refractive power of the lens increases
• a clear image is formed on the retina
Distant vision (>6 m away)
 Ciliary muscles relax
 Sclera goes back to normal
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position
Suspensory ligaments
become taut
Tension on the lens
increases
The lens becomes less
convex
The refractive power of the
lens decreases
The clear image is formed
on the retina
Changing lens thickness
 The lens is slightly
elastic, its relaxed
state is short and fat.
Cilary
muscles are
attached to the lens, when
contracted they pull the
lens thin
Pupil reflex/
pupillary mechanism
 Your eye can be
damaged by
harsh light.
 Your iris controls
light allowed into
the eye by
changing the size
of the pupil
In bright light
 The circular muscles of the iris contract
 The radial muscles relax
 The pupil constricts
 The amount of light entering the eye is
reduced
In dim light
 The radial muscles of the iris contracts
 The circular muscles relax
 The pupil dilates
 The amount of light entering the eye is
increased
Adaptation of the eye
 The sclera is tough and non-elastic to protect the inner
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structures of the eye.
The cornea is transparent allowing light to enter the eye.
The choroid has a brown pigment which absorbs the light
thus preventing reflection of light within the eye.
The iris has circular and radial muscles which alter the size of
the pupil.
The ciliary muscles help to change the shape of the lens for
accommodation
The suspensory ligaments holds the lens in position
The lens can refract the light to focus clearly on the retina
The retina has rods and cones, to receive the stimulus of
light
The aqueous humor maintains the shape of the eye, supplies
the eye with oxygen and nutrients and plays a minor role in
the refraction of light.
Visual defects
 Short-sightedness
 Causes:
 Eyeball being too long
 Inability of the lens of the eye to become less
convex (rounded).
 Treatment
 Wear glasses with a concave lens.
 Contact lenses
 Laser treatment.
Long-sightedness
(farsightedness)
 Causes
 Eyeball being too rounded
 Inability of the lens to become more convex –
common in the elderly
 Treatment
 Wear glasses with convex lens
 Astigmatisation
 The front surface of the cornea is curved more in one
direction than \in the other.
Symptoms:
Distortion or blurring of images at all
distances
Headache and fatigue squinting and eye
discomfort and irritation
Treatment
Prescription glasses are required if the
degree of astigmatisation is great enough to
cause eye strain and head ache, or
distortion of vision.
 Cataracts
 Refers to: The cloudy,
opaque part of the
lens.
 not clear
understanding of its
causes.
 Treatment:
 Surgical removal of
the lens.
 replacing the lens
with a synthetic lens.
VISION WITH A CATARACT
The ear
 Draw label and give functions -:- pg 229(you
should be used to this by now so don’t
complain)
Main functioning of the ear
 Hearing
 balance
Structure and function
 The ear consists of three regions:
 Outer ear
 Middle ear
 Inner ear
Oval
window
Round
window
Hearing
Path of sound
 Sound waves → Pinna →auditory canal
→tympanic membrane (vibrates) →hammer
→anvil →stirrup →oval window → fluid of
the cochlea (as pressure waves) →organ of
Corti coverts stimuli to impulses → auditory
nerve→ brain (cerebrum)
Adaptations
 Pinna --- large and traps sound waves
 Cerumen (wax) and hairs --- prevents small organisms
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from entering the ear
Cerumen --- prevents the tympanic membrane from
drying out
Hammer --- transmits vibrations from the eardrum to the
anvil then stirrup.
Stirrup transmits vibrations to the oval window into the
inner ear
The Eustachean tube allows air to move in and out of the
middle ear, thus maintaining equal pressure on either
side of the ear drum
Amplificication
 Decreasing size of structures as you move to
inner ear causes amplification.
Balance
The ear is responsible for balance in the following ways:
1. The cristae in the semicircular canals are stimulated by
changes in the direction and speed of movement
2. The maculae in the sacculus and utriculus are
stimulated by changes in the position of the head
When stimulated, the cristae and maculae convert the
stimuli received into nerve impulses.
The nerve impulses are transported along the auditory
nerve (vestibular branch) to the cerebellum to be
interpreted.
The cerebellum then sends impulses to the muscles to
restore balance.
Hearing defects
Middle ear infection
Cause:
 Excess fluid in the
middle ear caused by pathogen infection.
Treatment:
 Inserting grommets
 Antibiotics
Deafness
Cause:
• Injury to parts of the ear, nerves or parts of brain
responsible for hearing.
 Hardened wax
 Hardening of ear tissues (e.g.ossicles).
Treatment:
 Hearing aids
 Cochlear implants
Hearing aids
Cochlear implants