Clear, concise, effective summary notes covering all points in Topic 15: Control and Coordination of the new 2022-24 CIE A Level Biology syllabus. A must-have revision tool that helped me achieve an A* in A-Level Biology.
Topic 15: Control and coordination
Endocrine system
● all of endocrine glands in body + hormones they secrete
● endocrine gland
○ group of cells that prod. & releases hormone(s)
○ good blood supply → get hormones into bloodstream
○ no ducts
● hormone
○ chemical substance prod. by endocrine gland & carried by blood → transmit info. from 1
part of organism to another → alter activity of target organ(s)
○ only affect cells w/ complementary receptors → bind
○ types of hormones
Peptides/small proteins Steroids
water-soluble lipid-soluble
cannot cross phospholipid bilayer can cross phospholipid bilayer
bind to receptors on cell membrane of target cells bind to receptors in cyto./nucleus of target cells
→ activate 2nd messengers inside cyto.
● neurones
○ features
■ axon – long fibre insulated by fatty sheath
■ myelin – fatty sheath made of Schwann cells
● ~⅔ motor & sensory neurones = unmyelinated
● encloses axon in many layers of cytoplasm
■ nodes of Ranvier – small uninsulated sections along axon
■ cell body – contains organelles & structure of neurones
■ dendrites – connect to other neurones
, ○ types of neurones
■ motor neurone
● CNS → effectors
● large cell body at 1 end w/in CNS
● nucleus in cell body
● many extensive RER in cell body
● many mito. in cell body, axon, axon terminals
● many highly-branched dendrites → large SA for axon terminals of other
neurones
■ sensory neurone
● receptors → CNS
● cell body branches off in middle of axon
● nucleus in cell body
● near source of stimuli/in swelling of spinal nerve = ganglion
■ intermediate/relay neurone
● connect sensory neurones & motor neurones
● entirely w/in CNS
● sensory receptor cells
○ features
■ respond to stimuli
■ = transducers – convert E. in 1 form → electrical impulse
■ often found in sense organs
■ some = specialised cells → detect specific type of stimulus, others = ends of
sensory neurones
○ example – chemoreceptors in taste bud for salt
1. Na+ from NaCl diffuse thru. highly-selective channel proteins in cell membranes of
microvilli of chemoreceptor cells → ↑ +tive charge → cell membrane depolarised
● ↑ +tive charge = receptor potential – change in resting pot. across
membrane of receptor cell
2. sufficient stimulation by Na+ → sufficient depolarisation → receptor pot. > threshold
potential → V-gated Ca2+ channels open
● if stimulus = weak → receptor pot. not as often > threshold pot. → ↓ freq. of
impulses
● if stimulus = v. weak → receptor pot. < threshold pot. → will not transmit
impulse
● eg. of all-or-nothing law – impulse only transmitted if initial stimulus
sufficient to ↑ membrane pot. > threshold pot.
● NB. threshold pot. often ↑ w/ continued stimulation → ↑ stimulus req. for
impulses
2+
3. Ca enter cyto. → stimulate exocytosis of vesicles containing neurotransmitters
from basal membrane of chemoreceptor
4. neurotransmitters stimulate action pot. in sensory neurone → transmits impulse to
brain
● nerve impulses
○ resting potential
■ inside of resting axon always has ~-70mV pot. diff. cf. outside
● ie. inside 70mV more negative cf. outside axon
■ factors maintaining resting pot.
The benefits of buying summaries with Stuvia:
Guaranteed quality through customer reviews
Stuvia customers have reviewed more than 700,000 summaries. This how you know that you are buying the best documents.
Quick and easy check-out
You can quickly pay through credit card for the summaries. There is no membership needed.
Focus on what matters
Your fellow students write the study notes themselves, which is why the documents are always reliable and up-to-date. This ensures you quickly get to the core!
Frequently asked questions
What do I get when I buy this document?
You get a PDF, available immediately after your purchase. The purchased document is accessible anytime, anywhere and indefinitely through your profile.
Satisfaction guarantee: how does it work?
Our satisfaction guarantee ensures that you always find a study document that suits you well. You fill out a form, and our customer service team takes care of the rest.
Who am I buying these notes from?
Stuvia is a marketplace, so you are not buying this document from us, but from seller nathanzhang. Stuvia facilitates payment to the seller.
Will I be stuck with a subscription?
No, you only buy these notes for £2.43. You're not tied to anything after your purchase.
