C3.1 Integration of body systems

How is system integration achieved?

Effective communication is needed within component parts of a system; this allows systems to coordinate so they can collectively perform the various functions of life

Hierarchy of organisations:

Cell, tissue, organ, organ system, organism

What is a cell?

Basic unit of life. Smallest structural unit that is capable of using energy to sustain itself. Cells in multicellular organisms differentiate to perform specific functions.

What are tissues?

Groups of cells that work together to perform a specific function. They can contain more than one type of cell. With the exception of blood, the cells in a tissue must adhere to each other and communicate with each other to coordinate a function.

What are organs?

Groups of tissues that work together to perform a unique function.

What is an organ system?

A group of organs with related functions that work together to carry out a larger function.

Examples of organ systems?

Respiratory, urinary, digestive

What is an organism?

A living individual made up of interconnected parts. Interactions and coordination between organ systems allow organisms to engage in processes necessary to sustain life.

When do emergent properties arise?

When parts of an organism interact and there is integration of body systems

Why are cheetahs effective predators?

Due to integration of their body systems. Systems make cheetahs more efficient predators: muscular, respiratory, nervous system

What is the endocrine system?

A network of glands that produce and secrete hormones into the bloodstream

What are hormones?

Chemical messengers that help regulate bodily functions

What is the nervous system?

Responsible for sending and receiving electrical impulses from different parts of the body

How do endocrine and nervous system communicate?

Through the hypothalamus which controls basic drives such as hunger and thirst

Similarities of endocrine and nervous

Both can stimulate or inhibit. Both respond to internal and external stimuli. Both rely on feedback mechanisms to maintain homeostasis. Both work together to regulate and coordinate bodily functions. Both use chemicals that bind to receptors (hormones and neurotransmitters). Both used for communication between parts of the body.

Differences between nervous and endocrine system?

Endocrine glands (secrete hormones) vs CNS and PNS.

Travel through bloodstream to target tissues vs send messages via neurones.

Involuntary functions controlled vs voluntary/involuntary actions

Responses are slow but long-lasting vs quick and short-lived responses.

General target cells throughout body vs localised effect to specific cells

Organs (pituitary, thyroid, adrenal gland) vs Brain, brain stem, spinal cord.

Circadian rhythm

the rhythm that allows humans to live a 24hr cycle

Pacemaker of the circadian rhythm?

Suprachiasmatic nucleus

Where is the SCN located

In the hypothalamus

Melatonin in the circadian rhythm?

Visible light synchronises the rhythm of the SCN to the 24hr cycle. Cells in the retina sense certain wavelengths of light and send neural impulses to the SCN. SCN stimulates release of melatonin when it is dark.

Where is melatonin released from?

Pineal gland

Effects of high melatonin levels?

Promotes sleep. Drop in core body temperature. Decrease in urinary production

Role of circulatory system

Transports a wide range of substances between tissues and cells

Structure of the CNS?

Brain, brainstem and spinal cord. Consists of grey matter (contains cell bodies) and white matter (contains unmyelinated axons)

What are the two components of the nervous system?

CNS and PNS

What is the purpose of the CNS

To receive information, interpret information and initiate a response.

Role of the spinal cord in the CNS?

Pathway for communication between brain and the rest of the body. Only responsible for unconscious processes.

Features of unconscious processes?

Involuntary, performed when either awake or asleep, secretion by glands and contraction of smooth muscle, coordinated by the brain and spinal cord.

Features of conscious processes?

Voluntary, performed only when awake, contraction of skeletal muscle, coordinated by cerebral hemispheres of the brain.

What is the primary motor cortex?

Sends signals via motor neurones to each striated muscle in the body. Allows for locomotion and posture control.

Upper motor neurone vs lower motor neurones?

Upper motor neurone carries impulse from cell body in brain to spinal cord. Lower motor neurone carries impulse from spinal cord to muscle fibres so they can contract.

What is the receptive field of central neurone?

It is the region of sensory input that influences the activity of a neuron.

What is two point discrimination?

The ability to perceive two nearby points of touch on the skin as separate stimuli rather than as a single point. Humans have evolved so that our receptors aren’t extra sensitive everywhere.

What is a requirement for two point discrimination?

Receptive fields of neurones must be very small. Receptors must be densely packed in a sensitive area.

What is the PNS?

Consists of nerves that connect the brain and spinal cord to organs. Role is to carry information to the CNS and away from the CNS towards effectors.

Two parts of the PNS?

Somatic nervous system that regulates voluntary movements. Autonomic nervous system regulates involuntary actions (heart rate and breathing rate)

Components of the somatic nervous system?

Motor neurones and sensory neurones

Components of the autonomic nervous system?

Parasympathetic, sympathetic, enteric nervous system (digestion).

What are receptors?

Specialised cells that detect specific types of stimuli from the environment and convert them into electrochemical signals.

Different types of receptors?

Photoreceptors (light, external condition). Mechanoreceptors (detects pressure, external condition). Thermoreceptor (detects temperature, external & internal). Chemoreceptor (detects concentration of carbon dioxide, external & internal). Nociceptor (responds to painful stimuli, external & internal). Stretch receptors (sense state of contraction in striated muscle, internal).

What is peristalsis?

Involuntary wave of muscle contraction which moves food bolus along the gut. Occurs in one direction away from the mouth.

What are the two muscles involved in peristalsis?

Outer longitudinal muscles and the inner circular muscles

Outer longitudinal muscles contract?

Contract in front of the bolus to reduce the length of that section. Forces food through the alimentary canal.

Inner circular muscles contract?

Contract behind the bolus to reduce the diameter of the lumen. Prevents food from moving backwards towards the mouth.

What parts of digestion are not controlled by the CNS?

Swallowing and defecation are voluntary and are not under CNS control

What is the central integrating system in the brain?

Receives information, processes and stores it. Coordinates responses.

What is the role of the cerebellum?

Coordinates unconscious motor functions (balance and muscle coordination)

What is the role of the cerebrum?

Initiates/coordinates movement. Regulates temperature. Plays a huge role in memory/language/speech.

Smooth muscle vs skeletal muscle contraction

Smooth muscle is controlled by autonomic nervous system whereas the skeletal muscle is controlled by somatic nervous system.

What is the role of the medulla?

In the brain stem. Controls unconscious activities (eg. Breathing and heart rate)

Role of pituitary gland and hypothalamus?

Maintains homeostasis via coordination of the nervous and endocrine system.

What role does the hypothalamus play in homeostasis?

Consists of a group of neurones called nuclei. Hypothalamus detects if conditions alter from normal in body and triggers the secretion of specific hormones from the pituitary gland depending on which nuclei are stimulated.

A specific example of homeostasis by the hypothalamus?

Osmoregulation and thermoregulation

What does the posterior pituitary gland secrete?

ADH and oxytocin

What does the anterior pituitary gland secrete?

LH, FSH, thyroid stimulating hormone, growth hormones

What is an example of a hormone that influences heart rate?

Adrenaline works directly on the sinoatrial node to increase heart rate and force cardiac contraction.

How does adrenaline increase heart rate?

Binds to adrenergic receptors in plasma membrane of target cells causing lots of different responses. Causes liver/muscle cells to break down glycogen into glucose which can be used in respiration. Bronchi/bronchioles dilate due to relaxation of smooth muscles (increases air flow during ventilation). Ventilation rate increases. Speeds up firing of sinoatrial nodes, increases heart rate. Increases strength of cardiac contraction. Vasodilation in arterioles that carry blood to skeletal muscles and liver. Vasoconstriction in arterioles that carry blood to gut, kidneys and skin.

What is ventilation rate?

The number of times air is inhaled and exhaled in a minute.

How is ventilation rate controlled?

Controlled by cells in respiratory centres in the medulla

What is the mechanism behind ventilation?

Nerves in the respiratory centres stimulate contraction of external intercostal muscles and diaphragm. Stretch receptors are activated from the expansion of lungs which causes temporary cessation of signals from the respiratory centre. Exhalation occurs passively.

How is blood pH lowered?

Carbon dioxide reacts with the water in blood to form carbonic acid. This dissociates to produced hydrogen ions which lower blood pH

What detects decreases in blood pH?

Chemoreceptors in the medulla, cartoid arteries and aorta detect decrease in pH and sends signals to respiratory centres in medulla.

What is the response to signals to respiratory centre in medulla due to low blood pH?

Respiratory centre sends impulses to diaphragm and external intercostal muscles to increases ventilation rate and depth of breathing. This decrease carbon dioxide concentration and allows more carbon dioxide to diffuse from alveoli blood capillaries to air in alveoli to leave the body. Blood pH returns to target range and signals from chemoreceptor stop.

Response to low blood pH overview?

Low blood pH detected by chemoreceptors → send signal to respiratory centre → send signal to diaphragm and intercostal muscles to increases ventilation rate → blood pH returns to target range.

What is the target range for blood pH in humans?

7.35-7.45

How is heart rate regulated in the brain?

Medulla has a cardiovascular centre. Parasympathetic nerve connects to sinoatrial node which slows heart rate down. Sympathetic nerve connects to sinoatrial node which speeds heart rate up.

What do baroreceptors detect?

high and low blood pressure.

What do plant phytohormones control?

Growth, development and responses to stimuli.

Examples of plant phytohormones ?

Auxin, Cytokinins, Gibberellins, Ethylene, Abscisic acid

What do auxins do?

Promote growth by the lengthening of cells.

Where are auxins produced?

Produced in coleophile (a protective sheath around the emerging root or shoot)

Distribution of auxins in normal conditions?

Auxin is distributed evenly along the shoot causing even vertical growth

What happens to auxin distribution if photoreceptors in coleophile detect a light stimulus?

Auxin moves to the opposite side to the light. Promotes growth so that plants grow towards the light.

How does auxin cause cell elongation?

Auxin stimulates proton pumps which increases H⁺ concentration in cell wall making it more acidic. The acidic environment activates enzymes which break the bonds between cellulose microfibrils in the cell wall. The loosening of the cell wall reduces its rigidity allowing it to stretch. The cell takes in water by osmosis and since the cell wall is more flexible, it results in cell elongation.

What do cytokinins do?

Promote cell division (cytokinesis) and ensure roots and shoots grow at equal rates. Promotes secondary growth (thickening) and help to control the rate of branching by a plant.

What do gibberellins do?

Trigger germination in dormant seeds.

What is ethylene responsible for?

Production of ethylene causes fruit ripening. Positive feedback mechanism. Helps synchronise the ripening of fruits and ensures it is rapid.

What happens when a fruit ripens?

Colour changes, softening of walls, conversion of starch into sugar. Once seeds are ready for dispersal, fruit ripens to attract animals.

Features of unripe fruit?

Flesh of immature fruit is hard and acidic. Fruits remain green and lacking in scent until seeds are fully developed.