C.3.1 - Integration of body systems

Body systems for communication

• Nervous system (receptors send signals to muscles) - electrical signals

• Endocrine system (glands respond to chemical signalling and release hormones) - hormones signal chemically, transported in bloodstream

Negative feedback control

The body’s system of retaining homeostatic conditions (body temmperature, glucose levels, blood pressure, digestion, etc.)

Emergent properties

Properties that appear in a complete organism but aren’t present in its individual components

Autonomic nervous system (ANS)

Part of nervous system that communicates with the brain without conscious knowledge

Target tissue of a hormone

The body tissue where a certain hormone produces an effect

Exp. of the nervous and endocrine systems working together

Release of adrenaline hormone is triggered by information passed on by the nervous system. Sensory organs transmit information to the nervous system, indicating that adrenaline is needed as part of a fight-or-flight response. ANS then sends impulses to the adrenal glands (upper kidney) to release adrenaline.

Nervous system characteristics

• Electrical impulses send messages

• Neurons are used to transmit and recieve impulses

• Parts control volontary actions, parts control involontary

• Responses are quick and short-lived

Endocrine system characteristics

• Hormones send messages

• Hormones travel through bloodstream

• Only involontary functions are controlled

• Responses are slow but long-lasting

Brain receptors (conscious level) - Cerebrum

• Photoreceptors - retina, process visual info

• Chemoreceptors - tongue, process tastes

• Thermoreceptors - skin, process temeperature changes

• Mechanoreceptors - inner ear, process loud vibrations

Brain receptors (subconscious level)

• Osmoreceptors - carotid artery, hypothalamus, regulate blood water levels and solute levels

• Baroreceptors - carotid artery, aorta, sense blood pressure changes

• Proprioceptors - muscles and joints, provide balance and coordination

How does the brain communicate with the body?

• Spinal nerves (31 paired nerves emerging from spinal cord)

• Cranial nerves (12 paired nerves connected to the brainstem)

Three main parts of the brain

• Cerebrum

• Cerebellum

• Brainstem

Cerebrum

• Divided into right and left cerebral hemispheres

• Each hemisphere contains frontal, temporal, parietal, and occipital lobes

• Controls conscious activities

  • Frontal lobe coordinates memory & learning activities

Cerebellum

Coordinates volontary movements; controls balance + equilibrium

Brainstem

• Relays impulses between cerebrum, cerebellum, and spinal cord

• Controls subconscious functions neccessary for life (e.g. medulla regulates breathing and heart rate)

Spinal cord cell types

• White matter (axons + neurons, carries neural impulses to and from the brain)

• Grey matter (neurons + synapses)

Reflex arc

Pathway of an impulse

Hormone def

• Produced in the glands

• Secreted into the bloodstream

• Acts on a target cell

Regions of spinal cord

• Cranial nerves (facial movement)

• Cervical region (head neck & upper body)

• Thoracic region (torso, hands & fingers)

• Lumbar region (legs)

• Sacral region (bowel & bladder, sexual function)

Transduction

Conversion of specific physical stimulus to electrical impulse (action potential)

Motor cortex, motor neurons

Part of the cerebrum where action potetials are sent from, neurons that carry action potentials to muscle tissue

Neuromuscular junctions

Synapses formed by motor neurons and muscle fibres — release neurotransmitters (acethylcoline) that create muscle contractions

Types of neurons

• Sensory: send sensory information to the brain via the CNS

• Motor: send action potentials to muscles via the CNS

• Inter: transport impulses through the CNS

Mixed nerves

Contain both sensory and motor neurons

Myelinated vs. unmyelinated neurons

Myelinated = have Schwann cells wrapped around the axon and “blank” areas in between called nodes of Ranvier — much faster transmission as impulses can skip between nodes of Ranvier.

Pain reflex arc

Nocireceptor - spinal nerve - interneuron

Resulting actions go directly to effector

Circadian rhythm

Pattern of behaviour or physiology based on a 24-hour cycle, controlled by the pineal gland

Adrenaline (epinephrine) effects

• Raises heart rate

• Dilates air passages to allow more oxygen to enter the lungs

• Dilates pupils

• Raises blood sugar: stimulates glycogen → glucose in the liver

• Increases blood supply to muscles

Hypothalamus

Part of the brainstem that connects the nervous and endocrine systems. Composed of neuclei (group of neurons that recieve the same kind of sensory information) and glandular cells, produce hormones that stimulate or inhibit further hormone release by the pituitary glands. Associated with the ANS and recieves action potentials from other parts of the body with those receptors.

Pituitary glands

Two lobes: posterior and antererior, which secrete different hormones and communicate differently with the hypothalamus. Produces ADH (antidiuretic hormone) which regulates water levels in blood.

Posterior pituitary hormones

Oxytocin & ADH

Anterior pituitary hormones

LH, FSH, TSH, GH & Prolactin

Baroreceptors & chemoreceptors located

Baro: opening of aorta & sinus of carotid artery

Chemo: in tissues near baro outside the blood vessels, capillaries off major arteries

Action potentials transferred from baro- and chemoreceptors to…

Medulla

Chemoreceptors in blood sensitive to…

• Oxygen levels

• pH

• Carbon dioxide levels

Resting ventilation rate controlled by…

Respiratory centres in the medulla, release spontaneous action potentials to diaphragm and intercostal muscles

Ventilation rate during exercise

Regulated by chemoreceptors in the medulla: blood is typically slightly alkaline, but exercise = higher rate of respiration = higher CO2 content in blood, which needs to be regulated

Nervous system & digestion

ENS (enteric nervous system) regulates peristaltic reflex (contractions moving food along alimentary canal) in an involuntary process.

Peristaltic reflex

Bolus (rounded mass of food) stimulates stretch receptors in the ENS. Stretch receptors synapse with relay neurons that synapse with two different types of motor neurons. One releases excitatory neurotransmitters, stimulating the muscle behind to contract, and one releases inhibitory neurotransmitters, stimulating the muscle ahead to relax.

How are hormones specialised to target cells/tissues?

Target cells/tissues have specialised receptors to recieve specific hormones

Heart rate control

• Sinus node (pacemaker cells) generate action potentials stimulating the heart to contract

• Adrenaline can stimulate the pacemaker cells to generate action potentials more frequently — causing an increase in heart rate

Feedback control of heart rate

• Baroreceptors & chemoreceptors sense heightened blood pressure and fall in pH, causes an increase in the firing rate of nerves to the medulla.

• Parasympathetic nerve signals to the SA node to decrease rate of depolarisation

• During contiuous activation, sympathetic nerves signal to the adrenal gland to secrete adrenaline (epinephrine), which then acts on the SA node to keep heart rate up

Depolarisation

The passing of an action potential through a neuron