Biology
nerves and stuff like that, advanced biology Michael kent
nerves and stuff like that, advanced biology Michael kent
Kartei Details
Karten | 41 |
---|---|
Sprache | English |
Kategorie | Biologie |
Stufe | Mittelschule |
Erstellt / Aktualisiert | 01.03.2017 / 02.03.2017 |
Weblink |
https://card2brain.ch/box/20170301_biology
|
Einbinden |
<iframe src="https://card2brain.ch/box/20170301_biology/embed" width="780" height="150" scrolling="no" frameborder="0"></iframe>
|
Lernkarteien erstellen oder kopieren
Mit einem Upgrade kannst du unlimitiert Lernkarteien erstellen oder kopieren und viele Zusatzfunktionen mehr nutzen.
Melde dich an, um alle Karten zu sehen.
low-frequency and high-frequency
ear can discriminate between different soundwaves because of different responsiveness of hair cells along the length of the cochlea.
base of the cochlea --> basilar membrae = narrow, thin and rigid --> high frequencies
apex of the cochlea --Y baislar membrane = wider and less rigid --> low frequency sounds.
perception of intensity or loudness
depend on the number of neurones that are activated an the frequency of their impulses.
sense of balance and information about position movement
come form the vestibular apparatus in the inner ear.
vestibular apparatus
The vestibular appartus consists of the semicircular canals, containing organs called cristae, and sacs called the saccule and utricle, containing organs called maculae.
semicircular canals
The inner ear has three semicircular canals, each lying in a different plane at right angles to the other two. --> changes of movement (accleration / deccleration) in any direction can be detected.
Each canal is filed with fluid (endolymph)and has a small swelling (ampulla) containing a sense organ.
sense organ (crista)
The sense organ called crista, has hair cells embedded in a gelatinous structure called a cupula. The cupula moves in response to movements of the endolymph canal, bending the cilia that project from the hair cells.
When the cilia bend
they produce generator potentials --> treshold level
saccule and utricle
two sacs in the vestibular aparatus contain sense organs called maculae , which are lined with hair cells sourrounded by a jelly-like fluid. Fine granules ove in response to changes in body positiion and bend the cilia on the hair cells. If the cilia bend in one direction, the frequency of nerve impulses increases, bending the cilia in the other direction decreases the frequency.
Where is the information from the vestibular apparatus transmitted?
The information from the vestibular appartus is transmitted to several parts of the cnetral nervous system: spinal cord --> body position, cerebellum --> smooth coordinated movements, higher centres of the brain --> control of eye movements
What are electrical signals called?
nerve impulses
resting neurone/resting potential
A resting neurone is so called because it does not convey a nerve immpulse, not because it is inactive. a resting neurone expends much eergy in maintaining a potenntial difference across its membrane.
measured: about - 70 milivolts.
During the resting potential, the inside of a neurone is negative relative to the outside because of an unequel distribution of charged ions.
distribution of particles of the neurone
On the outside, sodium ions Na+, chloride ions Cl- and calcium IOns Ca2+ are present in higher concentrations than inside the cell. By contras the inside of the cell has a higher concentration of potassium ions K+ and organic anions (negative ions).
Why distriubtion of these ions?
This unequela distribution of ions results from a combination of active transport and diffusion of sodium and potassium ions across the cell membrane, and the inability of large organic anions to pass out of the cell. A sodium-potassium pump actively transports sodium ions out of the neurone and potassium ions in.
This wouldn't be enough. --> membrane is about 50 times more permeable to potassium ions than to sodium ions. potassium ions --> able to diffuse back out of the cell down their concentration gradient. sodium ions diffuse back ionto the cell only very slowly. --> negative electrical charge inside
When the stimulus is applied...
the axon becomes depolarised (the inside becomes temporarily less negative). If the stimulus is strong enought (exceeds the threshold level) --> action potential occurrs.
--> complete change of the charge across the nerve cell:
- interior becomes positively charged relative to the outside
- +35 milivlts
- potential difference then back down, undershoots the resting potential and finally returns to it.
entire action potential --> 7 miliseconds
repolarisation
The return of the potential difference towards the resting potential.
Stimulus (stimuli)
All living organisms must be able to detect changes in their environment and respond appropriately. Changes in the environment are called stimuli. A stimulus may be in either the external environment (outside the organism) or the internal environment (inside the organism).
A nerve impulse occurs when the resting potential across the membrane of a neurone has a sufficiently high stimulus. A stimulus is any disturbance in the external or internal environment which changes the potential difference across a membrane.
may be: chemical, thermal / electrical / change in light intensity.
Sensitivity
the ability to respond appropritaley to stimuli, is one of the characteristic featers of life. Each organism has its own sepcific type of sensitivity that imporves its chances of survival.
sense organs
In large multicellular animals such as mammals, stimuli are detected in sense organs.
effectors
Body part or cell that reacts to a stimulus in a particular way, or a cell substance in the body that produces an effect. p. ex. In a reflex the effector muscle acts before your brain is able to think.
and organs tat respond to sttimuli are called effectors.
What do the interconnections form?
The interconnections form circuits which enable us to control our muscles, think, remember and even sturd our own brains.
In mammals there are two major systems that convey information:
the nervous system and the endocrine system. Both involve cell signaling.
All animal nervous systems are fast-acting communication systems containing nerve cells, (name?)
neurones, which convey information as nerve impulses (electrochemical signals)
Neurons take various forms but each has ?
a cell body, containing a nucles, and nerve fibres, long extensions that transmit nerve impulses rapidly from one part of the body to another.
Fibres carrying impulses aeay from the cell body are called
axons
those carrying impulses towards the cell body are called
dendrons
Apart from the main nerve fibres there may be
small dendrons (dendrites) extending from the cell body
sensory neurones
In mammals, sensory neurones carry messages from peripherial sense organs to a central nervous system (CNS) consisiting of the brain and spinal cord. The CNS acts as an integration centre and processes information from many sources.
Motor neurones
Motor neurones convey instructions from the CNS to effector organs (mainly muscles and glands). can convey information rapidly and over considerable distances
mylein sheath
These fast-conducting neurones are enclosed along most of their lengt by a thick insulating material called the mylein sheat.
Schwann cells
The mylein sheat is produced by special supporting cells called Schwann cells. The sheath is essentially a series of cell membranes, each produced by a Schwann cell and wrapped many times around the axon.
-
- 1 / 41
-