Biology - C6

Nervous/endocrine systems, negative feedback/homeostasis and thermoregulation

Homeostasis

The maintenance of the bodies internal environment despite changes in the external environment or the bodies rate of activity.

Homeostasis

Concentration of CO2 and ions, pH of blood, temperature, blood glucose and water controlled by…

Negative feedback

How is homeostasis controlled?

Negative feedback loop

A deviation from normal creates a set of responses that bring the system back to normal / a change which reverses the effect of a particular stimulus to maintain stability.

Effectors

Organs, glands, muscle or any other structure that responds to bring the variable back to the set point - told by control centre to counteract the deviation/correct imbalance.

Receptors/sensors

Respond to light, heat, pain or other external or internal stimulus - detects change /imbalance and sends message to control centre.

Control centre

Compares factor (change/imbalance) against the set point in homeostasis.

Stimulus

A change in the internal or external environment - detected by receptor/sensor.

Electromagnetic receptors

Photoreceptors (light) and thermoreceptors (heat) are both … - neural receptors.

mechanoreceptor

Detects sound, touch, pressure, balance - neural receptor.

chemoreceptors

Detected from food/environment - neural receptor.

Nocireceptors

Detects pain - neural receptor.

Central nervous system

Made up of brain and spinal cord which contains ‘interneurons’ which are relay neurons.

Skull and vertebrae

What protects the central nervous system.

Somatic nervous system

Part of the PNS - voluntary movements and sensory perceptions - what we experience - system

Peripheral nervous system

Part of the nervous system that lies outside the brain and spinal cord and communicates between the brain and body - somatic or autonomic

Autonomic nervous system

PNS: parasympathetic (rest and digestion), sympathetic (fight or flight) and enteric (gastrointestinal) - what is the system

Sensory/afferent neurons

Neurons that carry information from the receptors to the central nervous system.

Motor/afferent neurons

Neurons that carry information from the central nervous system to effectors - muscles/organs/glands.

Neuron

Electrically excitable cells that transmit signals throughout the body - electrical or chemical components - connects to effector organs (+ synapse stuff) - nerve cell

Sensory neurons

After a stimulus which is used first, motor or sensory neurons?

Motor neurons

Which neuron (sensory or motor) is used by the central nervous system to control effectors and cause response to a stimulus.

Interneurons

CNS: a neuron which transmits impulses between other neurons.

Dendrites

The ‘branches’ of the neuron that collect information from other cells and sends it into the cell body.

Cell body/soma

Keeps the cell alive and contains nucleus and organelles - main section (circle)

Axon

Part that transmits information from cell body via action potential to the axon terminal - long section

Schwann cells

Produce myelin sheath

Myelin sheath

Fatty tissue surrounding axon fibre, acts as an insulator that allows faster transmission of electrical impulses - goes faster as it stops the diffusion of action potential out of the axon

Nodes of Ranvier

Gaps in the myelin sheath, contain voltage gated Na+ and K+ channels - rejuvenates action potential between jumps (saltatory conduction)

Axon terminal

End of axon, leads to synapses and contains neurotransmitters.

Neurotransmitters

Chemical that carries messages/signals from one neuron to the next cell

Action potential

A rapid sequence of changes in the potential difference across a membrane to transmit information from one part of the body to another.

-70mV

The resting potential of a neuron (volts)

Electrochemical gradient

The difference in charge between the outside of a neuron, which is more positive, and the inside, which is more negative - in the axon

Sodium-potassium pump

When in a resting state it maintains the concentration gradient/electrochemical gradient by pumping 3 Na⁺ out and 2 K⁺ in

Voltage gated channels

Protein channels in the neural membrane that are closed at -70mV and open during a change in the electrical potential across the membrane - Na+ and K+ have them

Negative

Is it more positive or negative inside a neutron at resting potential.

Positive

Is outside of the neuron more positive or negative at resting potential.

Axon stimulation

Causes sodium voltage gated channels to open so Na+ goes into the neuron so it becomes less negative (-70mV to -55mV) - can be environmental stimulus or neurotransmitter binding to dendrite.

Depolaristion

When the potential difference reaches -55mV more Na V.G.C open to cause rapid ___ and causes potential difference to be +30mV - more Na+ in neuron

-55mV

The threshold value

Repolarisation

After about 1 millisecond all Na V.G.C close and Ka V.G.C open so Ka+ diffuse out of axon/neuron - potential difference drops to -80mV

Hyperpolarisation

Occurs due to lag in closing K V.G.C - membrane potential is at -80mV so sodium-potassium pump brings it back to -70mV (resting)

Action potential

What travels down the neuron as the -55mV potential difference triggers depolarisation in one section which then triggers it in the next - wave movement

Resting, axon stimulation, depolarisation, repolarisation, hyperpolarisation and resting

Order the stages of action potential (including resting)

Nodes of Ranvier

Where are the Na and Ka V.G.C on the neuron

x100

By how much does having myelin sheaths increase the transmission speed of action potentials

refractory period

Action potential travels in one direct in the axon (dendrite to synapse) due to the…

repolarisation

The refractory period occurs because the voltage gated channels close due to the potential difference not being -55mV after ___ which is -80mV

sensory neuron

The nature of stimulus (light/heat/pain) is deduced due to the position of the ___ ___ on the body

strength

The brain interprets the ___ of a stimulus due to the frequency of the action potential and the number of neurons

Synapse

The gap between the axon terminal and the next neuron

neurontransmitters

What is the action potential converted to in the synapse - chemical messages

Action potential depolarisation in the membrane

What causes the Ca2+ V.G.C to open in the synapse.

pre-synaptic neuron

The ___ neuron sends chemical messages to the post-synaptic neuron across the synapse

post-synaptic neuron

The pre-synaptic neuron sends chemical messages to the ___ across the synapse

synaptic vesticles

What are the neurotransmitters inside in the pre-synaptic neuron.

terminal bud

other name for axon terminal

synaptic vesticles

After Ca2+ enters the pre-synaptic neuron what does it interact with.

dock

What does the synaptic vesticle do at the membrane after interacting with the Ca2+

neurotransmitters

What is released into the synapse when the vesticle docks at the membrane of the pre-synaptic neuron.

target cell

other name for post-synaptic neuron

receptors

What do neurotransmitters bind to after being released from the pre-synaptic neuron across the synapse to the post-synaptic neuron.

Action potential

Receptors (5) receive the neurotransmitter (4) which affects what? (increase or decrease)

Ligand-gated channels

Other name for receptors on the post-synaptic neuron / open after neurotransmitters bind to receptors???

Excitatory neurotransmitters

Chemical message that stimulates an action potential (depolarisation) or tiggers action in the cell - more positive in cell = action potential

Inhibitory neurotransmitters

Chemical message that causes hyperpolarisation (flow of K+ and Cl+ out of cell) to reduce the message - more negative = resting

Reabsorbed, diffused, broken down

After neurotransmitters are used by the receptor what three things can happen? ___ back into the post-synaptic neuron, ___ away from site or ___ by enzymes.

The endocrine system

A collection of glands that produce hormones to regulate metabolism, growth and development, sexual function, reproduction, mood, sleep, etc.

Hypothalamus, pituitary glands and pancreas

Three organs in the endocrine system.

neurohormones

Hormone produced by the hypothalamus

pituitary glands

Target of neurohormones from the hypothalamus

Antidiuretic hormone

Hormone produced by the pituitary glands

kidneys

Target of antidiuretic hormones from the pituitary glands

glucagon and insulin

Hormones produced by the pancreas

liver

Target of glucagon from the pancreas

Liver and most cells

Target of insulin from the pancreas

Through the bloodstream

How do hormones travel to cells after they are excreted from the organ.

Nervous system

Which is more fast acting endocrine or nervous?

Endocrine system

Which message lingers nervous or endocrine?

Nervous system

Is nervous or endocrine sent electrically via neurons?

Endocrine system

Is nervous or endocrine sent chemically via hormones?

Increase water reabsorption

What do the pituitary glands instruct the kidneys to do using antidiuretic hormones?

Increase the blood glucose levels

What does the pancreas instruct the liver to do using glucagon?

Glycogen

What does the glucagon convert into glucose to increase blood glucose levels?

Decrease blood glucose levels

What does the pancreas instruct the liver and most cells to do using insulin?

Glycogen formation

What does the insulin simulate in the kidneys to decrease blood glucose levels?

binds to receptors

To affect target cells hormones ___ to ___ on the cell

stimuli

What controls the release of particular hormones? - pressure, light, etc

stimuli, hormones

Presence of metabolic products and other hormones and stimulation by the autonomic nervous system are all ___ that control the release of ___

permeability, enzymes, cell organelles, gene production

Hormones influence target cells by changing the ___ of a membrane, affecting ___ in a membrane, affecting the ___ ___ or activating ___ ___

link, control homeostasis

The role of the hypothalamus is to ___ nervous and endocrine systems and ___

Pituitary glands

What other organ in the endocrine system is controlled by the hypothalamus (using hormones)?

control centre

The hypothalamus can be call the ___ of the endocrine system

hormones, chemicals, blood

Hypothalamus collects information from other parts of the brain by monitoring ___ and ___ in the ___ passing through.

master gland

The pituitary gland is also called ___ because it produces many hormones and controls the function of some other endocrine glands.

Thermoregulation

The maintenance of internal body temperature

36.1-37.2

Average internal body temperature for an adult human

38.5

Fever

35

Hypothermia - body temperature