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Human NS (Brain (Structure In skull, in membrane (meninges) Bs of…
Human NS
Brain
Structure
In skull, in membrane (meninges)
Bs of connected neurones; yoghurt consistency
Cerebral Cortex: (80% of brain)
Conscious, Intelligence, Language, Memory
Hi develop; Right for Left, Left for Right
Cerebellum:
Muscular activity, balance co-ordination (no initiation)
Damaged = jerk movement; comm. w/ cerebral
Medulla:
Automatic activities - breathing, digestion etc.
Brain Damage: Phineas Gage
Can help ID roles of the brain
Changes in personality, memory match parts
25 y/o in accident w/ rod through head (1848)
From polite, hardworking to rude, liable for 13 yrs
Scientists now ID he lost part for social inhibitions
Stimulation
Top of skull removed - no nerve endings in brain
Patient is left awake, can describe feelings
Hunger, fear, thirst from artificial e.stimulation
MRI Scan
Magnetic Resonance Image
Can show affected brain areas
Link regional damage to lose of speech etc.
Can now record while humans do simple tasks
Problems
Many chem. for synapses;
many neurones per function
Easily damaged, destroyed;
difficult to treat, investigate disorders
Surgery can cause damage;
drugs don't always reach
Reflex Actions
Reason
Avoid danger w/ fast reaction; auto & rapid
Also manage basic body functions (breathing etc.)
Don't involve thought to reduce duration of damage
Works
Inc. sensory, motor, relay neurones (in CNS)
Relay usually in Spine as shortcut to motor
Arc - Receptor, sensory, relay, motor, effector
Time between reflex & response is ASAP
Synapses
Gaps between neurones - aren't connected
Impulses can't leap; Chem. diffuse to pass impulse
Chemicals are slower than e.impulse
Reflex arc
Pin prick - skin stimulus to e.impulse to sensory
Synapse chem. diffuse to relay (new e.impulse)
Another diffuse to motor to effector (muscle)
Cause contractions in muscle to avoid pin
Co-ordinator in Spine rather than brain
Impulse still reaches brain, after reflex
Principles
of HS
Actions
Internal environment - conditions inside body
Many processes to keep things constant
Cell, body regulation for optimum functioning
Enzymes have optimum conditions (temp, pH)
Control all cell functions - building blocks of life
Conditions: Temperature, Water content, Glucose conc.
Collaboration
HS inc. co-ordination, control; awareness of changes
Exercise = hotter muscles; Meal = hi-er blood sugar levels
Hot water = water, salt loss in sweating
Response inc. Auto control system; nerve response in NS
Chem. response in Hormone system - involves many organs
Control System
Receptors: (part of NS or HS)
Detect stimuli - changes in in/external environment
Co-ordinate Centre: (mostly brain)
Receive, process stimuli; send & co-ordinate signals
Brain controls NS, HS parts, Spine, Pancreas
Effectors: (Muscles/Glands)
Bring response to stimuli; restore optimum conditions
Eye
Problems
Accommodation
Light from afar -
almost parallel
Light from close by -
strong divergence
Lens make sure you on different sources
Distant = less convex/flatter
- less refract
Close = more convex/rounder
- more refract
Lens harden w/ age; close reading gets difficult
Myopia
Short-sighted
: clear close focus, blurred long focus
Light focused before retina - maybe
lens are too round
Maybe eye is particularly long;
Concave
lens need
(Spread light rays apart)
Hyperopia
Long-sighted
: clear distant focus, blurred close focus
Light focused after retina -
lens is too flat/thin
Convex
lens needed (bring light rays together)
Eye
Technology
Contact lenses
Placed on eye surface, mostly invisible, good for physical
Hard
- Taken off at night, sterilised, last a while
Soft
- Flexible, comfortable, shorter life, sterilise overnight
Disposable
- Worn for a day, then thrown away
Laser Eye Surgery
For adults w/ stable vision
(eyes stopped growing)
Myopia
:
Reduce cornea thiccness, refracts less
Hyperopia
:
Change cornea curve, more effective refract
Lens Replacement Surgery
Add lens implant, fix defect permanently
Or
replace lens w/ artificial lens
(both can have infection)
Can damage retina
, Cataracts can form w/ natural lens
Human NS
NS
Uses e.signals (1-120 m/s)
Help avoid danger, find food, maybe a mate
Sensitive to stimuli - changes in int/external enviro.
Receptor Cells - similar to most cells, same parts
Receptors clustered in special sense organs (eyes etc.)
Many diff. sensory receptors; CNS co-ordinates response
Works
Stimulus to e.impulse; impulse through neurones
Through sensory neurones to CNS (brain, spine);
CNS to motor neurones; neurones to effectors
Muscles contract, Glands secrete w/ impulse
Eye
Parts
Sclera
- Clear tough coating on eye front
Ciliary Muscles
- Can change lens' shape
Blind Spot
- Where optic nerve leaves eye
Iris
- Muscle to control the size of the pupil
Suspensory ligaments
- Holds lens in place
Retina
- Light-sensitive, images to e.impulse
Lens
- Disk, focuses light from pupil to retina
Cornea
- Begins light refraction, protects eye
Pupil
- Allows appropriate light amount in eye
Optic Nerve
- Sens e.impulses, retina to brain
Works
Eye keeps shape w/ clear jelly
Refraction
: Light changes direction
Adjustments of lens shape for distance
Lens focuses
image on retina upside down
Brain interprets impulses
as right way up